Global Burden of Meconium‐Stained Amniotic Fluid: A Systematic Review and Meta‐Analysis of Prevalence With Descriptive Synthesis of Determinants

ABSTRACT

Background and Aims

Meconium‐stained amniotic fluid (MSAF) is a common intrapartum finding associated with adverse perinatal outcomes. Comprehensive global estimates of its prevalence and determinants are lacking. This systematic review and meta‐analysis aimed to estimate the global pooled prevalence of MSAF and classify its associated factors.

Methods

We searched Ovid MEDLINE, Scopus, Web of Science, Embase, Cochrane Library, SID, and Google Scholar up to January 1, 2026, for observational studies reporting MSAF prevalence or associated factors. Pooled prevalence with 95% CI was calculated using a random‐effects model with Logit transformation. The Knapp–Hartung adjustment and 95% prediction interval were applied. Heterogeneity was quantified using I ². Subgroup analyses and meta‐regression explored heterogeneity sources. Quality was assessed using the Newcastle‐Ottawa Scale. Due to high heterogeneity, meta‐analysis of risk factors was not feasible; findings were summarized descriptively.

Results

Fifty‐one studies were included (44 for prevalence; 1,414,705 births). The global pooled prevalence was 13.0% (95% CI: 10.8–15.6%; prediction interval: 6.9–23.1%; I ² = 99.71%). Prevalence doubled in low‐income compared to high‐income countries (22.2% vs. 11.1%; p < 0.001). Significant variations were observed by continent (p < 0.001), country (p < 0.001), and meconium consistency (p = 0.004). Meta‐regression showed a significant positive association with mean gestational age (β = 0.077, p = 0.014). Twenty‐two risk factors were classified into four domains: Social/Structural (inadequate antenatal care, delayed referral, low income), Intrapartum (prolonged/obstructed labor, PROM, oligohydramnios, non‐reassuring fetal heart rate pattern [NRFHRP]), Maternal (hypertensive disorders, diabetes, anemia), and Fetal/Physiological (advanced gestational age, primiparity, macrosomia). The strongest modifiable determinants were intrapartum factors—NRFHRP (adjusted odds ratio [AOR] up to 21.9), obstructed labor (AOR up to 24.6)—and system‐level barriers, particularly delayed referral (AOR up to 15.3). Intrauterine growth restriction (IUGR) showed no statistically significant association in any adjusted analysis.

Conclusion

MSAF affects one in eight pregnancies globally, with a higher burden in low‐income settings. Four‐domain classification identifies actionable targets—intrapartum monitoring failures and health‐system barriers—for quality improvement. Meconium consistency grading offers a simple risk stratification tool. Addressing these factors, particularly in resource‐limited settings, can reduce preventable perinatal morbidity and align with global health equity goals.

Abbreviations

CI

confidence interval

MAS

meconium aspiration syndrome

MeSH

Medical Subject Headings

MOOSE

Meta‐analysis of Observational Studies in Epidemiology

MSAF

meconium‐stained amniotic fluid

NICU

Neonatal Intensive Care Unit

NOS

Newcastle‐Ottawa Scale

PRISMA

Preferred Reporting Items for Systematic Reviews and Meta‐Analyses

PROM

premature rupture of membranes

PROSPERO

International Prospective Register of Systematic Reviews

1. Introduction

Meconium is a sterile, dark green‐to‐black material that begins to accumulate in the fetal gastrointestinal tract from approximately the third month of gestation [1, 2]. It consists of desquamated epithelial cells, mucin, lanugo, vernix caseosa, bile pigments, and intestinal secretions [2, 3]. Functional maturation of the external anal sphincter around 16 weeks of gestation reduces meconium passage, which becomes uncommon between 20 and 34 weeks [2, 4]. Meconium staining of the amniotic fluid (MSAF) results from antenatal meconium passage into the amniotic cavity [5]. While this may occur physiologically in term and post‐term pregnancies, it is more frequently associated with fetal hypoxia, cord compression, or other hypoxic‐ischemic insults that stimulate peristalsis and anal sphincter relaxation [6, 7, 8, 9].

MSAF is associated with adverse maternal and neonatal outcomes [10, 11]. Meconium concentration is an important factor in adverse outcomes [12], with thicker MSAF associated with higher rates of maternal infections, including chorioamnionitis [13]. Mothers with MSAF are twice as likely to require operative delivery [14]. Their infants have significantly higher rates of low Apgar scores, birth asphyxia, neonatal sepsis, meconium aspiration syndrome (MAS), NICU admission, and neonatal mortality [14, 15, 16]. However, a meta‐analysis demonstrated that intrapartum prophylactic amnioinfusion in MSAF cases reduces MAS, low Apgar scores, neonatal acidosis, and cesarean delivery rates [15]. MSAF occurrence is significantly linked to pregnancy‐induced hypertensive disorders, as well as intrapartum events including prolonged or obstructed labor, induction of labor, and premature rupture of membranes [17, 18, 19].

Despite its clinical importance, our understanding of the true global burden of MSAF remains incomplete and geographically restricted. Two recent systematic reviews and meta‐analyses from Ethiopia—Gashaw et al. (2024) [19] and Chuko et al. (2025) [18]—have reported regional prevalence estimates of approximately 20% in sub‐Saharan Africa. However, these estimates lack the geographical breadth to represent the global situation. A comprehensive global synthesis that quantifies MSAF prevalence across different income levels, continents, and healthcare settings remains lacking. Furthermore, no previous study has systematically explored the substantial geographical and socioeconomic disparities in MSAF burden or synthesized modifiable health‐system factors—such as inadequate antenatal care, delayed referral, and low income—alongside well‐established biological risk factors.

To address these critical gaps, we conducted the first global systematic review and meta‐analysis of MSAF prevalence with the following objectives: (1) to quantify prevalence across different income levels and continents, (2) to systematically explore geographical and socioeconomic disparities, and (3) to synthesize modifiable health‐system factors alongside well‐established biological risk factors, thereby offering actionable evidence for health system strengthening.

2. Materials and Methods

This systematic review and meta‐analysis were conducted according to the Meta‐analysis of Observational Studies in Epidemiology (MOOSE) guidelines [20] (Supporting File 1) and are reported following the PRISMA 2020 statement [21] (Supporting File 2). The study protocol was registered in PROSPERO (ID: CRD42025638830) prior to commencement.

2.1. Eligibility Criteria

Included studies met the following criteria:

Observational studies (including retrospective/prospective cohort or population/hospital‐based cross‐sectional studies) reporting the prevalence and/or associated factors of MSAF in pregnant women. Studies were excluded if they were case‐control, reviews, conference abstracts, letters, or randomized trials. Studies focusing solely on the outcomes of MSAF (e.g., MAS) were also excluded.

2.2. Search Strategy

A comprehensive systematic search was performed in international databases (Ovid MEDLINE, Scopus, Web of Science, Embase, Cochrane Library), Persian databases (SID), and Google Scholar. The search utilized a combination of Medical Subject Headings (MeSH) terms and free‐text keywords, such as: “meconium‐stained amniotic fluid” OR “MSAF” OR “meconium aspiration” AND “prevalence” OR “incidence” OR “epidemiology” OR “risk factor.” The search was limited to Persian and English language publications and covered all studies published up to January 1, 2026. Manual searching of reference lists was also performed. The complete search strategy is detailed in Supporting File 3.

2.3. Study Selection

Following duplicate removal, titles and abstracts were screened independently by two reviewers (MN & TM). The full texts of potentially eligible studies were then retrieved and assessed. Any discrepancies were resolved through discussion or by consultation with a third reviewer (ST).

2.4. Data Extraction

Data were extracted independently by two reviewers (MN & TM) using a standardized form. Extracted information included: study ID, country, World Bank income group, continent, study design, MSAF diagnostic method, delivery mode, inclusion criteria, mean gestational age (weeks), number of MSAF cases, total sample size, prevalence, and reported associated factors.

2.5. Quality Assessment (Risk of Bias)

The methodological quality of included studies was appraised using the Newcastle‐Ottawa Scale (NOS), adapted for cross‐sectional and cohort designs [22]. Two independent reviewers (MN & TM) performed the assessment. Using the nine‐star rating system, studies were classified as high (seven to nine stars), moderate (four to six stars), or low (zero to three stars) quality. Disagreements were resolved by consensus or by a third reviewer (ST).

2.6. Statistical Analysis

All meta‐analyses were performed using STATA software, version 18. A random‐effects model with the DerSimonian–Laird estimator and Logit transformation was used to calculate the pooled prevalence with a 95% confidence interval (CI). The Knapp–Hartung adjustment was applied to provide more accurate standard errors and confidence intervals in the presence of high heterogeneity. The 95% prediction interval was calculated to estimate the range within which the true prevalence of MSAF would fall in a future individual study. This interval provides clinically meaningful information about the expected variability in different settings and addresses the limitations of a single pooled estimate.

Heterogeneity was quantified using the I ² statistic (percentage of total variation across studies due to heterogeneity) and τ ² (between‐study variance). I ² values of 25%, 50%, and 75% were considered as low, moderate, and high heterogeneity, respectively.

To explore the substantial heterogeneity (I ² = 99.71%), we performed prespecified subgroup analyses (geographical, methodological, and population characteristics), meta‐regression (publication year, sample size, mean gestational age, and cesarean section percentage), and exploratory sensitivity analyses (leave‐one‐out and quality‐based excluding moderate‐quality studies). Publication bias was assessed visually using funnel plots and statistically via Egger's and Begg's tests. All statistical tests were two‐sided, and a p‐value < 0.05 was considered statistically significant. All statistical analyses were performed in accordance with the recommendations of Assel et al. [23] for the proper analysis, reporting, and interpretation of clinical research. Due to the high heterogeneity among studies reporting factors associated with meconium‐stained amniotic fluid, a meta‐analysis was not feasible. Therefore, we presented the findings using a descriptive analysis.

3. Results

3.1. Search Results

Following the PRISMA guidelines, a systematic screening and study selection process was conducted. A total of 1925 records were identified through database searches. After removing 645 duplicate records, 1281 unique records were screened based on their titles and abstracts. Of these, 1222 records were excluded for not meeting the inclusion criteria. Subsequently, the full texts of 59 reports were sought for retrieval, and all were successfully obtained (n = 0 not retrieved). After a detailed full‐text evaluation, 8 reports were excluded for the following reasons: four studies [24, 25, 26, 27] due to irrelevant study designs (Case‐Control) and three studies [28, 29, 30, 31] because they focused solely on specific outcomes (MSAF) without addressing the primary research questions. Ultimately, 51 studies met all inclusion criteria and were included in the final analysis of this systematic review. This selection process is summarized in Figure 1 (PRISMA flow diagram).

FIGURE 1.

PRISMA flow diagram of study selection process. Flow diagram showing the identification, screening, eligibility, and inclusion of studies. Of 1925 records identified, 51 studies met the inclusion criteria after screening and full‐text review.

3.2. Characteristics of Included Studies

A total of 51 studies were included, originating from high‐income, upper‐middle‐income, lower‐middle‐income, and low‐income countries across Asia, Africa, Europe, North America, South America, and Oceania. Study designs included retrospective cohorts, prospective cohorts, and hospital‐based cross‐sectional studies. Detailed characteristics of each included study, including country, income level, continent, study design, sample size, prevalence estimates, and diagnostic methods, are presented in Table 1. Methodological heterogeneity in MSAF diagnosis and grading was observed across studies; detailed information on diagnostic criteria and grading systems is also provided in Supporting File 4, Table S1.

TABLE 1.

Characteristics of the included studies.

Study ID	Country	Income group	Continent	Meconium grade	Study design	Delivery mode	Inclusion criteria	Mean GA (weeks)	MSAF Cases/Total sample size (Prevalence)
Osava et al. 2012 [41]	Brazil	Upper middle income	South America	Not Specified	Cross‐sectional study	Both	Births at an in‐hospital birth center in São Paulo, March–April 2005. Women with habitual risk pregnancy.	Not reported	289/2437 (11.9%)
Oyelese Y et al. 2006 [55]	USA	High income	North America	Not Specified	Retrospective cohort study	Both	All pregnancies with clinically diagnosed MSAF (Meconium‐Stained Amniotic Fluid) in 2004. Routine umbilical arterial (UA) sampling and placental pathology for MSAF cases.	39.7	12.0% (766/6403)
Beyene BN et al. 2024 [48]	Ethiopia	Low income	Africa	Not Graded	Facility‐based cross‐sectional study	Not Reported	Women who gave birth at West Guji public hospitals (gestational age ≥ 28 weeks). Excluded: fetal death, severe maternal illness, incomplete records.	NR	29.4% (99/314)
Özlü Akkuş F et al. 2022 [44]	Turkey	Upper middle income	Asia	Not Specified	Prospective cohort study	Both	Singleton, term (≥ 37 weeks) pregnancies with cephalic presentation in active labor (cervical dilation ≥ 6 cm). Excluded: chronic maternal diseases, pregnancy complications, fetal anomalies, prior cesarean/uterine surgery, breech presentation.	39.53	43.0% (151/351)
Tamang PB et al. 2024 [65]	Nepal	Lower middle income	Asia	Thick: 52.8% (140/265) Thin: 47.2% (125/265)	Hospital‐based retrospective cross‐sectional study	Vaginal: 27.9% (74/265) Cesarean: 72.1% (191/265)	All neonates born with MSAF (Meconium‐Stained Amniotic Fluid) at Nepal Medical College Teaching Hospital from Jan 2021 to Dec 2022.	NR	6.35% (265/4171)
Fang ZJ et al. 2020 [66]	China	Upper middle income	Asia	Not Specified	Retrospective cohort study	Vaginal delivery only	All patients with vaginal delivery at the hospital between Jan 2013 and Dec 2018. Excluded: cesarean delivery, multiple pregnancies, abnormal coagulation profile, concomitant liver/kidney disorders.	38.81	24.8% (13,686/55,197)
Abraham K et al. 2018	India	Lower middle income	Asia	Thin: 84.5% (169/200) Thick: 15.5% (31/200)	Prospective cohort study	Both	Primigravidae, > 37 weeks, singleton, cephalic, MSAF (Meconium‐Stained Amniotic Fluid) identified after admission. Excluded: ROM (Rupture Of Membranes)/fever prior to admission, malpresentation, preterm, multiple gestation, HIV+.	39.51	11.2% (469/4158)
Rahman MM et al. 2022 [32]	Bangladesh	Lower middle income	Asia	Grade I: 14.8% (27/182) Grade II: 28.0% (51/182) Grade III: 57.1% (104/182)	Hospital‐based prospective observational study (prospective cohort)	MSAF group: Vaginal: 31.8% (58/182), Cesarean: 68.2% (124/182).	Pregnant women in labor at ≥ 37 weeks, singleton, cephalic presentation with MSAF. Excluded: twin pregnancy, eclampsia, APH (Antepartum Hemorrhage), IUFD (Intrauterine Fetal Demise), congenital malformations, non‐cephalic presentation, preexisting maternal cardio‐pulmonary disease, unknown LMP/early ultrasound.	39.2	NR
Karpe NS et al. 2025 [7]	India	Lower middle income	Asia	Moderate	Observational, non‐interventional, cross‐sectional study	Cesarean section only	Singleton pregnancy, term (≥ 30 weeks), cephalic presentation, cesarean delivery for fetal distress (abnormal CTG per NICE (National Institute for Health and Care Excellence) guidelines).	NR	34.0% (68/200)
Christopher GL. 2020 [47]	India	Lower middle income	Asia	Grade I: 5.1% (141/2750) Grade II: 2.4% (66/2750)	Retrospective study	Both	Singleton live births at Shifa Hospital, Bangalore, from Jan 1, 2015 to May 31, 2017. Excluded: twin deliveries and stillbirths.	NR	7.5% (207/2750) Thin: 5.1% (141/2750) Thick: 2.4% (66/2750) MAS (Meconium Aspiration Syndrome): 1.8% (49/2750)
David AN et al. 2006 [42]	Nigeria	Lower middle income	Africa	Thick: 77.5% (62/80) Thin: 22.5% (18/80)	Prospective descriptive study	NR	Consecutive live singleton neonates of all gestational ages born to booked mothers at Lagos University Teaching Hospital (Mar–Jun 2003). Excluded: stillbirths, multiple births, gross congenital anomalies.	NR	20.4% (80/393)
Paz Levy D et al. 2019 [67]	Israel	High income	Asia	Not Specified	Population‐based retrospective cohort study	Vaginal and Cesarean. Cesarean rate: 13.7% (Combined)	All singleton deliveries at Soroka University Medical Center between 1991–2014. Excluded: congenital malformations, perinatal mortality cases for long‐term analysis.	39.01	14.7% (35,897/243,725)
Dereje T et al. 2023 [49]	Ethiopia	Low income	Africa	Grade I: 12.0% (9/75) Grade II: 48.0% (36/75) Grade III: 40.0% (30/75)	Hospital‐based cross‐sectional study	NR	Women who gave birth at term (37–41 + 6 weeks) at Adama Hospital Medical College. Excluded: unknown GA, preterm, post‐term (≥ 42 wks), multiples, malpresentation, congenital anomalies.	39.25 weeks	23.9% (75/314)
Balchin I et al. 2011 [36]	United Kingdom	High income	Europe	Not Classified	Large population‐based cohort study	Vaginal breech delivery had highest OR (OR = 4.71). Model adjusted for mode of delivery.	All singleton live births weighing at least 500 g at 24 or more completed weeks of gestation in NW London maternity units (1988–2000).	NR	16.3% (81,405/499,096) Preterm: 5.1% Term: 16.5% Postterm: 27.1% By Race: Black: 22.6%, South Asian: 16.8%, White: 15.7%.
Balogh DC et al. 2025 [68]	Hungary	High income	Europe	Not Specified	Single‐center retrospective observational study	Cesarean: 87.3% (207/237)	Preterm infants born at ≤ 32 gestational weeks or with birthweight ≤ 1500 g who had complete placental histopathological evaluation. Excluded congenital malformations.	28.6 weeks	9.3% (22/237)
Carr BL et al. 2018 [39]	Australia	High income	Oceania	Not Specified	Retrospective correlation study	Vaginal: 78.5% (2387/3041) Cesarean: 21.5% (654/3041) Emergency Cesarean: Not Reported (OR = 1.74)	All women who gave birth to a live, singleton, term (≥ 37 weeks) infant at a tertiary hospital in Melbourne in 2014. Excluded if maternal country of birth or type of amniotic fluid data was missing.	39.45	22.1% (672/3041) Australian‐born: 19.8% (224/1131) Non‐Australian born: 23.5% (448/1910)
Shukla OS et al. 2019 [69]	India	Lower middle income	Asia	Not Specified	Prospective observational study	Vaginal: 38.3% (232/606) Cesarean: 61.7% (374/606)	All live neonates delivered through meconium‐stained amniotic fluid at the neonatal unit of a tertiary care hospital in Vadodara.	NR	NR
Tantu T et al. 2024 [35]	Ethiopia	Low income	Africa	Not Specified	Multicenter cross‐sectional study	Emergency Cesarean Section only	Mothers who gave birth via emergency cesarean section at two hospitals in south central Ethiopia (Aug–Oct 2022). Excluded: fetal lethal anomaly, absent fetal heartbeat at admission, breech presentation, mother unable/unwilling to provide history.	NR	31.4% (275/875)
Becker S et al. 2006 [70]	Germany	High income	Europe	Not Specified	Retrospective cohort study with matched‐pair control group	Vaginal: Combined: 79.2% (1779/2246) Cesarean: Combined: 13.5% (303/2246) Operative Vaginal: Combined: 10.1% (226/2246)	Singleton, cephalic, ≥ 37 weeks, trial of vaginal birth. Excluded: primary C‐section, multiples, severe maternal disease, preeclampsia, fetal malformations.	40.1	10.0% (1123/11,226)
Rodríguez Fernández V et al. 2018 [71]	Spain	High income	Europe	Yellow (thin): 41.3% (208/503) Green (moderate): 55.1% (277/503) Thick: 3.6% (18/503)	Retrospective cohort study	Vaginal: Combined: 65.8% (2362/3590) Cesarean: Combined: 17.8% (639/3590) Operative vaginal: Not Reported	All singleton deliveries ≥ 24 weeks' gestation during 2015. Exclusion: multiple gestation.	NR	14.0% (503/3590)
Sriram S et al. 2003 [38]	USA	High income	North America	Not Specified	Population‐based retrospective cohort study	Both (Cesarean delivery associated with higher MAS risk)	Non‐Hispanic Black and Non‐Hispanic White live births with birth weight > 2.5 kg. Excluded cases with unknown MSAF/MAS status.	NR	Overall: 6.0% By Race (1998–2000): Non‐Hispanic Black: 8.1% (80.8/1000) Non‐Hispanic White: 4.9% (49.2/1000)
Chhetri UD et al. 2020 [50]	Nepal	Lower middle income	Asia	Thick: 44.1% (89/202) Thin: 55.9% (113/202)	Hospital‐based, descriptive, cross‐sectional study	Vaginal: 47.0% (95/202) Cesarean: 40.6% (82/202) Instrumental: 12.4% (25/202)	All inborn neonates delivered with MSAF at Lumbini Medical College Teaching Hospital. Excluded: stillbirths, congenital malformations, multiple gestations.	NR	13.6% (202/1478) MAS: 14.8% (30/202)
Shakya P et al. 2022 [72]	Nepal	Lower middle income	Asia	Grade II (Moderate): 67.0% (61/91) Grade I (Thin): 18.7% (17/91) Grade III (Thick): 14.3% (13/91)	Descriptive cross‐sectional study	Vaginal: 24.17% (22/91) Cesarean: 75.82% (69/91)	All babies born to women in labor who had completed > 37 weeks of gestation at Patan Academy of Health Sciences. Excluded: non‐cephalic presentation, twin pregnancies, stillbirth, maternal comorbidities (hypertension, eclampsia, APH (Antepartum Hemorrhage), IUFD (Intrauterine Fetal Demise)).	NR	5.35% (91/1699)
Shrestha S et al. 2022 [73]	Nepal	Lower middle income	Asia	Thin: 35.06% (27/77) Moderate: 31.17% (24/77) Thick: 33.77% (26/77)	Descriptive cross‐sectional study	Vaginal: 35.07% (27/77) Cesarean: 64.93% (50/77)	All newborns born in Kathmandu Medical College Teaching Hospital within the study period. Excluded: parental non‐consent, birth injuries, congenital malformations, multiple gestations, preterm babies.	NR	13.37% (77/576)
Hailemariam HA et al. 2020 [46]	Ethiopia	Low income	Africa	Grade I: 40.0% (12/30) Grade II: 33.3% (10/30) Grade III: 26.7% (8/30)	Hospital‐based cross‐sectional study	Total cohort (n = 248): Vaginal: 56.9% (141/248) Cesarean: 43.1% (107/248) Instrumental: 19.0% (47/248)	Mothers with term (≥ 37 wks), cephalic presentation delivery at SPHMMC (St. Paul's Hospital Millennium Medical College). Excluded: preterm delivery, breech presentation, critical maternal condition, unwillingness to participate.	NR	12.1% (30/248)
Dohbit JS et al. 2018 [74]	Cameroon	Lower middle income	Africa	Thick: 52.1% (111/213) Light: 47.9% (102/213)	Prospective cohort study	MSAF group: Vaginal: Not Explicitly Stated, Cesarean: 44.6% (95/213) Clear AF group: Vaginal: Not Explicitly Stated, Cesarean: 22.5% (48/213)	Pregnant women with term (37–42 wks), singleton, cephalic presentation, ruptured membranes admitted for labor at two tertiary hospitals. Excluded: preterm/post‐term, breech/other malpresentations, multiple gestation, elective cesarean, unknown LMP (Last Menstrual Period), IUFD (Intrauterine Fetal Demise).	39.45	11.15% (265/2376)
Mazor M et al. 1998 [75]	Israel	High income	Asia	Not Specified	Retrospective cohort study	Vaginal: Combined: ~79.0% (3849/4872) Cesarean: Combined: ~19.3% (939/4872)	Consecutive patients with preterm delivery (24–36 wks), singleton, vertex presentation, intact membranes. Excluded: lack of prenatal care, antepartum fetal death.	34.25	5.7% (276/4872) Incidence by GA: 24–27 wks: 2.6%, 28–31 wks: 7.8%, 32–36 wks: 5.6%
Bouchè C et al. 2018 [76]	Italy	High income	Europe	Thin and Thick (Distribution not provided)	Retrospective cohort study	Vaginal delivery only	All women who had a vaginal delivery at the study center between 24 and 44 weeks of gestation. Excluded: cesarean deliveries, cases with missing data on amniotic fluid color or postpartum blood loss.	NR	14.8% (10,997/74,144)
Kashikar S et al. 2021 [77]	India	Lower middle income	Asia	Thin: 57% (183/321) Thick: 43% (138/321)	Prospective observational study	Thin MSAF: Vaginal: 78.1% (143/183), Cesarean: 21.9% (40/183) Thick MSAF: Vaginal: 39.9% (55/138), Cesarean: 60.1% (83/138)	Live singleton, term (> 37 wks), cephalic pregnancy. Excluded: preterm, APH (Antepartum Hemorrhage), malpresentation, previous CS/myomectomy, multiples, congenital malformations, IUFD.	NR	10.29% (321/3117)
Abate E et al. 2021 [37]	Ethiopia	Low income	Africa	Not Specified	Hospital‐based cross‐sectional study	MSAF group: Vaginal: 43.6% (65/149), Cesarean: 56.4% (84/149) Clear AF group: Vaginal: 61.3% (280/457), Cesarean: 38.7% (177/457)	Singleton pregnancy, gestational age ≥ 28 weeks, admitted for labor at Felege Hiwot Referral Hospital. Excluded: breech presentation, unknown GA, fetal death on admission, congenital malformations.	NR	24.6% (149/606)
Tefera M et al. 2024 [45]	Ethiopia	Low income	Africa	Grade I: 67.0% (124/185) Grade II: 18.5% (34/185) Grade III: 14.5% (27/185)	Institutional‐based cross‐sectional study	Total cohort (n = 610): Vaginal: 87.22% (532/610), Cesarean: 12.78% (78/610) MSAF group mode of delivery not provided for entire group.	All women who gave birth at selected North Shoa Zone Hospitals with gestational age > 28 weeks. Excluded: breech presentation, congenital malformations.	NR	30.3% (185/610)
Porwal NP et al. 2020 [53]	India	Lower middle income	Asia	Thin and Thick	Retrospective observational study	NR	All MSAF live births born to singleton pregnancy (booked cases in KIMSDU) irrespective of maternal age, parity, risk factors, presentation and stage of labor. Excluded: unbooked mothers, stillbirths, congenital birth defects, multiple gestations, babies referred from other hospitals.	NR	Booked deliveries: 8.53% (363/4257) Total deliveries: 7.13% (363/5609)
Rodavsky G et al. 2021 [78]	Israel	High income	Asia	Not Specified	Population‐based retrospective cohort study	Vaginal: Combined: ~86.2% (210,061/243,682) Cesarean: Combined: ~13.6% (33,151/243,682)	Singleton deliveries at Soroka University Medical Center (1991–2014). Excluded: congenital/chromosomal malformations, multiple pregnancies. Perinatal mortality cases excluded from long‐term respiratory morbidity analysis.	39.0	14.7% (35,892/243,682)
Patel S et al. 2020 [79]	India	Lower middle income	Asia	Grade 1, 2, 3	Prospective observational study	NR	Laboring mothers with meconium‐stained amniotic fluid (MSL) and singleton pregnancy who delivered at the institute. Excluded: non‐consent, IUFD (Intrauterine Fetal Death), non‐cephalic presentation, multi‐fetal gestation.	NR	NR
Tran SH et al. 2003 [80]	USA	High income	North America	Thin: 8.8% (3,784/43,200) Moderate: 5.5% (2,396/43,200) Thick: 4.6% (1,993/43,200)	Retrospective cohort study	Clear fluid group: Operative delivery: 32.2% MSAF group: Operative delivery: 41.6%	All deliveries ≥ 37 weeks gestational age at a single community hospital. For chorioamnionitis analysis: excluded elective cesarean deliveries.	NR)	Overall: 18.9% (8173/43,200) Thin: 8.8%, Moderate: 5.5%, Thick: 4.6%
Hiersch L et al. 2016 (Study 1) [81]	Israel	High income	Asia	Not Specified	Retrospective cohort study	MSAF group: Vaginal: 71.8% (3512/4893), Cesarean: 11.7% (576/4893), Operative Vaginal: 16.5% (805/4,893) Control group: Vaginal: 82.5% (32,716/39,651), Cesarean: 10.3% (4098/39,651), Operative Vaginal: 7.2% (2837/39,651)	Singleton pregnancies at term (37–41 + 6 wks) attempting vaginal delivery. Excluded: high‐risk conditions (multiple gestation, non‐cephalic, fetal anomalies, hypertensive disorders, diabetes, oligohydramnios, SGA, maternal chronic diseases, chorioamnionitis, abruption).	39.2	10.9% (4893/44,544)
Hiersch L et al. 2016 (Study 2) [82]	Israel	High income	Asia	Not Specified	Retrospective cohort study	Total MSAF cohort (n = 3399): Vaginal: ~87.9% (2988/3399), Cesarean: ~8.5% (289/3,399), Operative Vaginal: ~13.2% (449/3,399)	Singleton pregnancies at term (37–41 + 6 wks) undergoing trial of labor. Excluded: high‐risk conditions (multiple gestation, non‐cephalic, fetal anomalies, hypertensive disorders, diabetes, oligohydramnios, SGA, maternal chronic diseases, chorioamnionitis, abruption, elective cesarean).	41.0	Overall in low‐risk cohort: 12.0% (3399/28,248) Prevalence increased with GA: 3.4% at 37 wks to 17.6% at 41 wks.
Abu Shqara R et al. 2025 [13]	Israel	High income	Asia	Light: 25.4% (561/2205) Intermediate: 64.7% (1426/2205) Thick: 9.9% (218/2,205)	Retrospective cohort study	Clear AF: Vaginal: 87.5% (12,028/13,745), Cesarean: 12.5% (1717/13,745) MSAF: Vaginal: ~84.8% (1870/2205), Cesarean: ~15.2% (335/2,205) Thick MSAF Cesarean: 21.6% (47/218)	Singleton term (≥ 37 wks) pregnancies undergoing trial of vaginal delivery. Excluded: multiples, major fetal anomalies, IUFD, bloody AF, elective CD (Cesarean Delivery), missing data.	40.0	13.8% (2205/15,950)
Wangwe PJ et al. 2024 [83]	Tanzania	Lower middle income	Africa	Not Specified	Cross‐sectional study	NR	Women at ≥ 28 weeks' gestation about to give birth to a singleton baby with longitudinal lie and cephalic presentation at Muhimbili National Hospital.	NR	8.7% (222/2566)
Addisu D et al. 2018 [43]	Ethiopia	Low income	Africa	Grade 3: 39.77% (35/88) Grade 2: 47.73% (42/88) Grade 1: 12.5% (11/88)	Facility‐based cross‐sectional study	Total cohort (n = 495): Vaginal: 75.5% (374/495), Cesarean: 24.2% (120/495), Instrumental: 2.4% (12/495)	All women who gave birth at term (≥ 37 weeks) at Felege Hiwot Referral Hospital. Excluded: breech presentation, intrauterine fetal death before labor onset.	38.95	17.8% (88/495)
Shekari M et al. 2022 [52]	Iran	Upper middle income	Asia	Not Specified	Retrospective cohort study	NR	Singleton pregnant mothers who gave birth at a tertiary hospital in Bandar Abbas. Excluded: mothers with bloody amniotic fluid.	NR	12.2% (1085/8888)
Reddy MS et al. 2025 [84]	India	Lower middle income	Asia	NR	Observational study	Thin MSAF: Vaginal: 92.54% (62/67), Cesarean: 7.46% (5/67) Thick MSAF: Vaginal: 69.70% (23/33), Cesarean: 30.30% (10/33)	Term pregnant women (> 37 weeks) with singleton, cephalic presentation and MSAF at or during labor. Excluded: malpresentations, multiples, congenital anomalies, APH, IUFD.	NR	NR
Al‐Sharif A et al. 2024 [85]	Yemen	Low income	Asia	Type I: 25.6% (10/39) Type II: 35.9% (14/39) Type III: 38.5% (15/39)	Retrospective, descriptive, quantitative study (Cross‐sectional)	Total cohort (n = 220): Vaginal: 83.6% (184/220), Cesarean: 16.4% (36/220) MSAF cases (n = 39): Vaginal: 87.2% (34/39), Cesarean: 12.8% (5/39)	All newborns (with or without meconium) born at Jibla University Hospital during the study period, via normal or cesarean delivery.	38.1	17.72% (39/220)
Sarwar N et al. 2023 [33]	Pakistan	Lower middle income	Asia	Thin and Thick	Cross‐sectional study	MSAF cases: Vaginal: 33% (20/60), Cesarean: 66% (40/60)	Patients > 37 weeks gestation with meconium‐stained liquor during labor and cephalic presentation. Excluded: newborns with congenital defects.	38.22	4.8% (60/1232) MAS prevalence within MSAF: 36% (22/60)
Divya NV et al. 2018 [40]	India	Lower middle income	Asia	Grade I: 19.6% (49/250) Grade II: 37.6% (94/250) Grade III: 42.8% (107/250)	Retrospective and prospective observational study (cross‐sectional case series)	Total MSAF cases: Vaginal: 43.6% (109/250), Cesarean: 56.4% (141/250) Cesarean rate increased with grade.	All live singleton pregnant women > 37 weeks with cephalic presentation and MSAF during labor at the study hospital. Excluded: APH, congenital malformations, preterm delivery, IUFD, non‐cephalic presentation.	41	NR
Asaye MM et al. 2023 [34]	Ethiopia	Low income	Africa	Grade III (Thick) specifically	Cross‐sectional study with mediation analysis	Total cohort: Vaginal: 55.5% (709/1277), Cesarean: 44.5% (568/1277)	Singleton live birth newborns in selected public hospitals. Excluded: twins, stillbirths, home births, readmitted neonates.	NR	Grade III MSAF prevalence: 7.1% (91/1277)
Murata T et al. 2022 [54]	Japan	High income	Asia	Not specified	Prospective nationwide birth cohort study (JECS)	MSAF group: Vaginal: 89.5% (1607/1796), Cesarean: 10.5% (189/1796) Reference group: Vaginal: 80.8% (48,664/60,195), Cesarean: 19.2% (11,531/60,195)	Singleton live births between 22 and 40 weeks' gestation. Excluded abortions, stillbirths, missing data, and pregnancies > 40 weeks.	NR	2.9% (1796/61,991)
Itzhaki‐Bachar L et al. 2021 [51]	Israel	High income	Asia	Specified (MSAF vs. Thick MSAF)	Retrospective cohort study	100% Cesarean Delivery (Elective)	All patients with singleton pregnancies who underwent an elective cesarean delivery during the study period.	Not NR	Overall MSAF: 3.5% (368/10,445) Thick MSAF: 0.3% (31/10,445)
Tolu LB et al. 2020 [16]	Ethiopia	Low income	Africa	Grade I: 35% (50/144) Grade II: 33% (48/144) Grade III: 32% (46/144)	Prospective cohort study	MSAF group: Vaginal: 44.4% (64/144), Cesarean: 44.5% (64/144), Instrumental: 11.1% (16/144) Clear fluid group: Vaginal: 72.9% (214/294), Cesarean: 22.6% (66/294), Instrumental: 4.5% (14/294)	Pregnant women in labor with ≥ 37 weeks gestation, viable singleton, cephalic pregnancies, and no known fetal anomalies.	NR	NR
Mohammad N et al. 2018 [86]	Pakistan	Lower middle income	Asia	Thin vs Thick Thick MSAF: 23.4% (35/149)	Retrospective study	Total MSAF cohort: Vaginal: 33.6% (50/149), Cesarean: 66.4% (99/149) Thick MSAF: Emergency C/S 71.4% (25/35)	Gestational age > 37 weeks, cephalic presentation, MSAF after spontaneous or artificial rupture of membranes. Excluded congenital anomalies.	39.1	7.85% (149/1898) MAS incidence: 12% (18/149)
Sori DA et al. 2016 [87]	Ethiopia	Low income	Africa	Grade 1: 25% (38/151) Grade 2: 40% (60/151) Grade 3: 35% (53/151) Moderate‐thick: 74.8% (113/151)	Cross‐sectional descriptive study	Total MSAF cases: Vaginal: 29.8% (45/151), Cesarean: 43.7% (66/151), Instrumental: 26.5% (40/151)	All laboring mothers with MSAF. Excluded: breech, non‐reassuring FHR on admission, IUD, presentation in second stage.	Majority 37–42 wks	15.4% (151/979)
Afiat et al. 2023 [88]	Iran	Upper middle income	Asia	Thick: 22.8% (26/114) Thin: 77.2% (88/114)	Cross‐sectional study	Total MSAF cohort (n = 114): Vaginal: 69.3% (79/114), Cesarean: 30.7% (35/114) Thick MSAF Cesarean higher (43.3% vs. 16.7%)	Singleton pregnancy, GA > 28 weeks, admission for labor pain, vaginal delivery. Excluded: Fetal anomaly, chorioamnionitis, genital herpes, cord prolapse, severe bradycardia, breech, previous cesarean, maternal diabetes/hypertension.	39	8.2% (114/1383)

Abbreviations: CTG, Cardiotocogram; FHR, Fetal Heart Rate; GA, Gestational Age; HIV, Human Immunodeficiency Virus; IUFD, Intrauterine Fetal Demise/Death; IUGR, intrauterine growth restriction; JECS, Japan Environment and Children's Study; KIMSDU, Krishna Institute of Medical Sciences Deemed University; LMP, Last Menstrual Period; MAS, meconium aspiration syndrome; MSAF, meconium‐stained amniotic fluid; MSL, meconium‐stained liquor; MUAC, Mid‐Upper Arm Circumference; NICE, National Institute for Health and Care Excellence (UK); NR, Not Reported; NRFHRP/NRFHP, non‐reassuring fetal heart rate pattern; OR, odds ratio; PIH, pregnancy‐induced hypertension; PPROM, preterm premature rupture of membranes; PR, prevalence ratio; PROM, premature rupture of membranes; ROM, Rupture of Membranes; SGA, Small for Gestational Age; SPHMMC, St. Paul's Hospital Millennium Medical College; UA, Umbilical Artery; vs, Versus; wks, weeks.

3.3. Methodological Quality Assessment

Of the 25 cross‐sectional studies, 15 (60%) were rated as high quality (7–8 stars) and 10 (40%) as moderate quality (5–6 stars). Among the 26 cohort studies, 14 (53.8%) were high quality (7–8 stars), and 12 (46.1%) were moderate quality (5–6 stars) (Supporting File 5, Table S1 and Table S2).

3.4. Meta‐Analysis of the Global Prevalence of MSAF

A meta‐analysis of 44 studies, comprising a total sample size of 1,414,705, yielded an overall pooled prevalence of MSAF of 13.0% (95% CI: 10.8% to 15.6%) using the Logit transformation with DerSimonian–Laird estimator and Knapp–Hartung adjustment. The 95% prediction interval ranged from 6.9% to 23.1%, indicating that the true prevalence of MSAF in a future individual study is expected to fall within this wide range across different settings. Considerable heterogeneity was observed among the included studies (I ² = 99.71%, τ ² = 0.1087, p < 0.001; Figures 2 and 3).

FIGURE 2.

Worldwide distribution of MSAF prevalence. World map presenting pooled prevalence estimates of MSAF by country. Darker shades indicate higher prevalence (e.g., Turkey: 43.0%; Ethiopia: 22.8%), while lighter shades indicate lower prevalence (e.g., Japan: 2.9%).

FIGURE 3.

Forest plot of the pooled prevalence of MSAF. Forest plot showing individual study estimates (squares) with 95% confidence intervals (horizontal lines) and the pooled estimate (diamond). The overall pooled prevalence was 13.0% (95% CI: 10.8–15.6%; I ² = 99.71%).

3.5. Subgroup Analyses

Subgroup analyses (Figure 4) identified several significant sources of heterogeneity. Tests for subgroup differences indicated that the country of study (Q = 9968.64, df = 20, p < 0.001), World Bank country income level (Q = 34.31, df = 3, p < 0.001), and continent (Q = 150.20, df = 5, p < 0.001) were significant moderators of prevalence estimates. In contrast, study design (cross‐sectional vs. cohort; Q = 3.65, df = 1, p = 0.06), MSAF diagnostic method (Q = 2.51, df = 1, p = 0.11), gestational age category (term‐only vs. mixed; Q = 0.03, df = 1, p = 0.86), and maternal risk category (low‐risk vs. mixed/high‐risk; Q = 0.17, df = 1, p = 0.68) did not show statistically significant differences between groups.

FIGURE 4.

Subgroup meta‐analysis of MSAF prevalence. Subgroup analyses by income level, continent, study design, diagnostic method, gestational age, and maternal risk category. Significant variations were observed by income level (p < 0.001), continent (p < 0.001), and country (p < 0.001). No significant differences were found for other subgroups (p > 0.05).

3.6. Geographical and Economic Variations

3.6.1. By Income Level (World Bank Classification)

The highest pooled prevalence was observed in low‐income countries (22.2%; 95% CI: 17.0–28.5; 9 studies), followed by upper‐middle‐income countries (17.4%; 95% CI: 6.8–37.7; 5 studies), high‐income countries (11.1%; 95% CI: 8.2–14.9; 16 studies), and lower‐middle‐income countries (10.0%; 95% CI: 7.3–13.7; 14 studies). The differences between income groups were statistically significant (Q = 34.31, df = 3, p < 0.001).

3.6.2. By Continent

The highest prevalence was found in Oceania (22.1%; 95% CI: 20.7–23.6; 1 study—Australia), followed by Africa (19.4%; 95% CI: 14.2–25.9; 11 studies), North America (15.1%; 95% CI: 0.6–84.7; 2 studies), Europe (13.3%; 95% CI: 10.0–17.4; 5 studies), South America (11.9%; 95% CI: 10.6–13.2; 1 study—Brazil), and the lowest in Asia (10.5%; 95% CI: 7.9–14.0; 24 studies). Differences across continents were statistically significant (Q = 150.20, df = 5, p < 0.001).

3.6.3. By Country

Prevalence estimates of MSAF varied widely across individual countries, with statistically significant differences between countries (Q = 9968.64, df = 20, p < 0.001). The highest estimates were reported from Turkey (43.0%; 1 study), China (24.8%; 1 study), Ethiopia (22.8%; based on 8 studies), and Australia (22.1%; 1 study). The lowest estimate was observed in Japan (2.9%; 1 study). Estimates derived from countries represented by only a single study should be interpreted with caution.

3.6.4. By Meconium Consistency

The highest prevalence was observed for moderate/Grade II meconium (5.7%; 95% CI: 4.0%–8.1%; 10 studies), followed by thin/light/Grade I (4.7%; 95% CI: 3.5%–6.3%; 19 studies). The lowest prevalence was estimated for thick/Grade III meconium (3.0%; 95% CI: 1.9%–4.7%; 21 studies). The 95% prediction intervals for each subgroup were: thin (1.4%–14.5%), moderate (2.3–13.5%), and thick (0.6%–13.1%), indicating substantial variability within each consistency category. The test for subgroup differences was significant (Q_b = 11.10, df = 2, p = 0.004), confirming that meconium consistency is a significant moderator of prevalence estimates (Table 2 and Figure 5).

TABLE 2.

Subgroup meta‐analysis of MSAF prevalence by meconium consistency.

Meconium consistency category	No. of studies	Pooled prevalence (95% CI)	I 2 (%)	Tau2	95% Prediction interval
Thin/Light/Grade I	19	4.7% (3.5–6.3)	98.12	0.317	1.4–14.5
Moderate/Grade II	10	5.7% (4.0–8.1)	97.39	0.140	2.3–13.5
Thick/Grade III	21	3.0% (1.9–4.7)	97.93	0.530	0.6–13.1

Note: Test for subgroup differences: Q_b = 11.10, df = 2, p = 0.004.

Abbreviations: CI, confidence interval; MSAF, meconium‐stained amniotic fluid.

FIGURE 5.

Subgroup meta‐analysis by meconium consistency. Forest plot presenting pooled prevalence estimates for thin (4.7%), moderate (5.7%), and thick meconium (3.0%). The test for subgroup differences was significant (Q_b = 11.10, df = 2, p = 0.004), confirming meconium consistency as a significant moderator.

3.7. Sensitivity Analysis

• 1. Leave‐one‐out analysis: Sequential exclusion of individual studies did not substantially alter the pooled prevalence, which remained stable between 12.6% and 13.4% (Figure 6).
• 2. Quality‐based analysis: Excluding 22 moderate‐quality studies (NOS score 4–6) and retaining only 22 high‐quality studies (NOS score ≥ 7) yielded a pooled prevalence of 14.3% (95% CI: 10.5–19.2%; I ² = 99.81%; 22 studies), with a 95% prediction interval of 3.7% to 41.8%. Although slightly higher than the main estimate (14.3% vs. 13.0%), the overlapping confidence intervals confirm robustness. The persistent high heterogeneity (I ² = 99.81%) suggests it is driven by clinical and methodological diversity rather than study quality alone.

FIGURE 6.

Leave‐one‐out sensitivity analysis. Forest plot showing pooled prevalence estimates after sequentially excluding each study. The overall prevalence remained stable between 12.6% and 13.4%, confirming the robustness of the pooled estimate (13.0%; 95% CI: 10.8–15.6%).

3.8. Meta‐Regression Results

Univariate meta‐regression analyses were performed to explore potential continuous moderators of MSAF prevalence (Table 3). A statistically significant positive association was found between MSAF prevalence and mean gestational age (β = 0.077, 95% CI: 0.015–0.138, p = 0.014), indicating that studies with higher mean gestational age reported higher prevalence estimates. No significant associations were detected with publication year (β = 0.010, 95% CI: −0.008 to 0.028, p = 0.26), cesarean delivery rate (β = −0.003, 95% CI: −0.007 to 0.002, p = 0.27), or sample size (β = 3.81 × 10⁻⁷, 95% CI: −9.05 × 10⁻⁷ to 1.67 × 10⁻⁶, p = 0.56). The lack of association between sample size and prevalence suggests that the observed heterogeneity is not driven by study size (Table 3).

TABLE 3.

Univariate meta‐regression analyses of potential moderators for MSAF prevalence.

Moderator	No. of studies	Coefficient (β)	Standard error	p‐value	95% CI
Publication year	44	0.010	0.009	0.263	−0.008 to 0.028
Cesarean delivery rate (%)	31	−0.003	0.002	0.270	−0.007 to 0.002
Mean gestational age (weeks)	20	0.077	0.031	0.014	0.015 to 0.138
Sample size	44	3.81 × 10−7	6.56 × 10−7	0.561	−9.05 × 10−7 to 1.67 × 10−6

Abbreviation: CI, confidence interval.

3.9. Assessment of Publication Bias

Visual inspection of the funnel plot revealed general symmetry (Figure 7). Formal statistical testing using Egger's regression test (β = 1.90, SE = 2.060, p = 0.36) and Begg's rank correlation test (z = 1.87, p = 0.06) found no statistically significant evidence of small‐study effects or publication bias.

FIGURE 7.

Funnel plot for publication bias. Funnel plot showing the distribution of study estimates against standard error. Symmetry was observed visually, and formal tests (Egger's: p = 0.36; Begg's: p = 0.06) found no significant evidence of publication bias.

3.10. Descriptive Synthesis of Factors Associated With Meconium‐Stained Amniotic Fluid

A total of 22 distinct risk factors for MSAF were identified across the included studies, reported in 1 to 14 studies each. These factors were classified into four domains based on their clinical and demographic characteristics: (I) Social and Structural Factors, (II) Intrapartum Factors, (III) Maternal Factors, and (IV) Fetal and Physiological Factors (Table 4).

TABLE 4.

Summary of risk factors for MSAF identified in included studies.

Domain	Subcategory	Risk Factor	Studies (n)	Range of effect	Study with highest estimate	Study with lowest estimate
I. Social and Structural Factors	Antenatal Care	Inadequate ANC (Un‐booked)	2	p < 0.05 to p < 0.001	Sarwar et al. [33] (p < 0.001)	Rahman et al. [32] (p < 0.05)
	Emergency System	Delayed referral (>1 h)	2	AOR: 2.28 to 15.258	Tantu et al. [35] (AOR = 15.258; 95% CI: 1.591–146.328)	Asaye et al. [34] (AOR = 2.28; 95% CI: 1.88–3.29)
	Socioeconomic	Low income	2	AOR: 1.04 to 2.03	Abate et al. [37] (AOR = 2.03; 95% CI: 1.18–3.51)	Balchin et al. [36] (AOR = 1.04; 95% CI: 1.02–1.06)
	Structural Equity	Racial/Ethnic disparities*	3	AOR: 1.81 to 8.38	Balchin et al. [36] – Black (AOR = 8.38; 95% CI: 2.44–28.78)	Sriram et al. [38] – Black US (AOR = 1.81; 95% CI: 1.80–1.82)
II. Intrapartum Factors	Dystocia	Prolonged labor	10	AOR: 1.81 to 7.5	Tefera et al. [45] (AOR = 7.5; 95% CI: 4.64–12.3)	Shukla & Swapna [47] (1.5% frequency)
		Obstructed labor	4	AOR: 0.49 (NS) to 24.61	Tantu et al. [35] (AOR = 24.61; 95% CI: 6.073–99.766)	Beyene et al. [48] (AOR = 0.49; 95% CI: 0.14–1.73, NS)
	Membrane and Amniotic Fluid	PROM	10	AOR: 1.47 to 10.06	Dereje et al. [49] (AOR = 10.06; 95% CI: 1.27–79.98)	Tefera et al. [45] (AOR = 1.7; 95% CI: 1.02–3.02)
		Oligohydramnios	6	AOR: 2.53 to 5.09	Dereje et al. [49] (AOR = 5.09; 95% CI: 1.29–20.03)	Abate et al. [37] (AOR = 2.53; 95% CI: 1.25–5.12)
	Fetal Monitoring	NRFHRP/Fetal distress†	8	AOR: 2.07 to 21.91	Abate et al. [37] (AOR = 21.91; 95% CI: 10.96–43.83)	Tantu et al. [35] (AOR = 2.068; 95% CI: 0.997–4.292)
	Fetal Position	Fetal malposition	3	AOR: 1.89 to 4.71	Balchin et al. [36] (AOR = 4.71; 95% CI: 4.16–5.33)	Asaye et al. [34] (AOR = 1.89; 95% CI: 1.14–3.16)
	Intervention	Induction of labor‡	6	PR: 1.83 (harm) to AOR: 0.53 (protective) — conflicting	Osava et al. [41] (PR = 1.83; 95% CI: 1.60–2.10)	Balchin et al. [36] (AOR = 0.53; 95% CI: 0.51–0.54, protective)
III. Maternal Factors	Vascular	Hypertensive disorders	8	AOR: 2.10 to 8.02	Tantu et al. [35] (AOR = 8.022; 95% CI: 1.634–39.372)	Asaye et al. [34] (AOR = 2.10; 95% CI: 1.49–2.95)
	Metabolic	Diabetes mellitus	4	AOR: 0.79 (NS) to p < 0.001	Sarwar et al. [33] (p < 0.001)	Shekari et al. [52] (AOR = 0.79; 95% CI: 0.33–0.91, NS)
	Hematologic	Anemia§	5	AOR: 0.17 (protective) to 1.37 (NS) — paradoxical	Tefera et al. [45] (AOR = 0.17; 95% CI: 0.07–0.4)	Abate et al. [37] (AOR = 1.37; 95% CI: 0.66–2.84, NS)
	Inflammatory	Inflammatory conditions/Infection	4	AOR: 1.62; p < 0.001	Balchin et al. [36] (AOR = 1.62; 95% CI: 1.50–1.74)	Murata et al. [54] (3.2% vs. 0.5%, p < 0.001)
	Bleeding	Antepartum hemorrhage	3	AOR: 8.43	Dereje et al. [49] (AOR = 8.43; 95% CI: 2.02–35.17)	Karpe et al. [7] (0.5% frequency)
IV. Fetal and Physiological Factors	Gestational age	Advanced gestational age	14	AOR/PR: 1.39 to 8.82	Dereje et al. [49] (AOR = 8.82; 95% CI: 3.18–24.49)	Balchin et al. [36] (AOR = 1.39; 95% CI: 1.38–1.40)
	Parity	Primiparity/Nulliparity	9	AOR/PR: 1.49 to 3.64	Tantu et al. [35] (AOR = 3.643; 95% CI: 1.215–10.921)	Abate et al. [37] (AOR = 0.62; 95% CI: 0.34–1.11, NS)
	Maternal age	Advanced maternal age	4	AOR: 1.26 to 5.63	Addisu et al. [43] (AOR = 5.63; 95% CI: 3.35–9.44)	Osava et al. [41] (NS)
		Adolescent maternal age	1	AOR: 3.07	Shekari et al. [52] (AOR = 3.07; 95% CI: 1.87–4.98)	—
	Fetal characteristics	Male fetal sex	2	AOR: 1.13	Balchin et al. [36] (AOR = 1.13; 95% CI: 1.11–1.15)	Murata et al. [54] (57.5% vs. 51.4%, p < 0.001)
		Birth weight/Macrosomia	3	PR/AOR: 1.20 to 1.47	Osava et al. [41] (PR = 1.47 for ≥ 4000 g)	Balchin et al. [36] (AOR = 1.20 for ≥ 90th percentile)
		IUGR‖	4	AOR: 2.4 to 3.04 (all NS)	Dereje et al. [49] (AOR = 3.04; 95% CI: 0.74–12.50, NS)	Addisu et al. [43] (AOR = 2.4; 95% CI: 0.775–7.70, NS)

Abbreviations: AOR, adjusted odds ratio; ANC, antenatal care; APH, antepartum hemorrhage; CI, confidence interval; IUGR, intrauterine growth restriction; NRFHRP, non‐reassuring fetal heart rate pattern; NS, not significant; OR, odds ratio; PR, prevalence ratio; PROM, premature rupture of membranes.

^*Racial/ethnic disparities reflect structural inequity in care access and quality, not biological determinism.

^† NRFHRP may represent concurrent fetal hypoxic stress rather than an independent antecedent risk factor.

^‡ Conflicting evidence on induction; likely reflects differences in indication, setting, and gestational age.

^§ The protective effect of anemia may reflect residual confounding; non‐significant findings in other studies support the need for higher‐quality research.

^‖ No adjusted analysis for IUGR reached statistical significance; current evidence is insufficient to confirm IUGR as a risk factor.

3.10.1. Domain I: Social and Structural Factors

3.10.1.1. Inadequate Antenatal Care

Two studies reported a significant association between inadequate antenatal care and MSAF [32, 33]. Sarwar et al. [33] observed that 86% of neonates with meconium aspiration syndrome were born to un‐booked mothers compared with 42% in the overall MSAF group (p < 0.001). Similarly, Rahman et al. [32] found that antenatal checkups were significantly less frequent in the MSAF group (83% vs. 94%, p < 0.05).

3.10.1.2. Delayed Referral

Delayed referral was identified as a significant risk factor in two multicenter Ethiopian studies [34, 35]. Tantu et al. [35] reported that mothers with referral time exceeding 1 h had 15.3 times higher odds of MSAF (adjusted odds ratio [AOR] = 15.258, 95% confidence interval [CI]: 1.591–146.328). Asaye et al. [34] similarly found that referred mothers had 2.28 times higher odds of MSAF (AOR = 2.28, 95% CI: 1.88–3.29).

3.10.1.3. Low Socioeconomic Status

Low income was significantly associated with MSAF in two studies [36, 37]. Abate et al. [37] reported that mothers with a monthly family income below 5000 Ethiopian Birr (approximately 185 USD) had 2.03 times higher odds of MSAF (AOR = 2.03, 95% CI: 1.18–3.51). Balchin et al. [36] found a modest but significant association with material deprivation (AOR = 1.04, 95% CI: 1.02–1.06).

3.10.1.4. Structural Equity and Racial Disparities

Three large cohort studies demonstrated significant racial and ethnic disparities [36, 38, 39]. Balchin et al. [36] found that Black women had 8.4 times higher odds (AOR = 8.38, 95% CI: 2.44–28.78) and South Asian women had 3.3 times higher odds (AOR = 3.31, 95% CI: 1.32–8.34) of MSAF compared with White women. Sriram et al. [38] reported an 80% higher risk among non‐Hispanic Black women compared with non‐Hispanic White women (AOR = 1.81, 95% CI: 1.80–1.82). Carr et al. [39] observed higher MSAF rates among non‐Australian‐born women (23.5% vs. 19.8%, p = 0.02), with women from Sub‐Saharan Africa having 2.1 times higher odds (AOR = 2.10, 95% CI: 1.12–3.92). These disparities reflect structural inequity in care access and quality, not biological determinism.

3.10.2. Domain II: Intrapartum Factors

3.10.2.1. Prolonged Labor

Prolonged labor was the most frequently reported factor, identified in 10 studies [34, 37, 40, 41, 42, 43, 44, 45, 46, 47]. The strongest association was reported by Tefera et al. [45], who found that labor duration of 15 h or more increased MSAF risk by 7.5‐fold (AOR = 7.5, 95% CI: 4.64–12.3). Addisu et al. [43] reported that labor exceeding 24 h was associated with 7.1 times higher odds (AOR = 7.1, 95% CI: 1.67–29.68). Additional studies reported AORs ranging from 1.81 to 5.44 [34, 35, 37, 46]. Significant associations were also reported by David et al. [42] (p = 0.001) and Özlü Akkuş et al. [44] (p = 0.002).

3.10.2.2. Obstructed Labor

Obstructed labor was examined in four studies [35, 42, 45, 48]. Tantu et al. [35] reported the strongest association (AOR = 24.614, 95% CI: 6.073–99.766). Tefera et al. [45] found an AOR of 3.6 (95% CI: 1.48–8.83), while David et al. [42] reported a highly significant association (p < 0.001). Beyene et al. [48] did not find a significant association (AOR = 0.49, 95% CI: 0.14–1.73).

3.10.2.3. Premature Rupture of Membranes

PROM was the second most frequently reported factor, identified in 10 studies [7, 33, 34, 42, 43, 45, 46, 48, 49, 50]. Dereje et al. [49] reported the strongest association (AOR = 10.06, 95% CI: 1.27–79.98). Hailemariam et al. [46] found that PROM was associated with 7.6 times higher odds (AOR = 7.6, 95% CI: 2.525–23.00), and prolonged PROM with 5.1 times higher odds (AOR = 5.1, 95% CI: 1.221–22.122). Beyene et al. [48] reported an AOR of 3.24 (95% CI: 1.79–5.88), while Tefera et al. [45] found an AOR of 1.7 (95% CI: 1.02–3.02). Asaye et al. [34] reported the lowest AOR of 1.47 (95% CI: 1.09–1.98).

3.10.2.4. Oligohydramnios

Six studies reported on oligohydramnios [37, 43, 46, 47, 49, 51]. Dereje et al. [49] reported the strongest association (AOR = 5.09, 95% CI: 1.29–20.03). Abate et al. [37] found an AOR of 2.53 (95% CI: 1.25–5.12). Itzhaki‐Bachar et al. [51] reported 2.2% in the MSAF group compared with 1.1% in controls (p = 0.001). Descriptive studies reported oligohydramnios in 2.8% to 9.4% of MSAF cases [43, 46, 47].

3.10.2.5. Non‐Reassuring Fetal Heart Rate Pattern (NRFHRP)/Fetal Distress

Eight studies reported on fetal heart rate abnormalities [35, 37, 40, 42, 45, 49]. Abate et al. [37] reported the strongest association with an AOR of 21.91 (95% CI: 10.96–43.83) for non‐reassuring fetal heart rate pattern. David et al. [42] reported an odds ratio of 10.75 (95% CI: 4.81–24.37). Tefera et al. [45] found that fetal tachycardia (AOR = 6.2, 95% CI: 2.41–16.3) and bradycardia (AOR = 3.1, 95% CI: 1.93–5.28) were both associated with MSAF. Tantu et al. [35] found AORs of 3.513 (95% CI: 1.633–7.556) for tachycardia and 2.068 (95% CI: 0.997–4.292) for bradycardia. NRFHRP may represent concurrent fetal hypoxic stress rather than an independent antecedent risk factor.

3.10.2.6. Induction of Labor

Six studies examined the association between induced labor and MSAF [16, 32, 36, 40, 41, 50]. Osava et al. [41] reported a prevalence ratio of 1.83 (95% CI: 1.60–2.10) for oxytocin use. Tolu et al. [16] and Rahman et al. [32] both found significant associations (p = 0.007). However, Balchin et al. [36] reported a protective effect for induced labor (AOR = 0.53, 95% CI: 0.51–0.54). The frequency of induced labor among MSAF cases ranged from 46.5% to 56.8% in descriptive studies [40, 50]. Conflicting evidence on induction likely reflects differences in indication, setting, and gestational age.

3.10.2.7. Fetal Malposition

Three studies reported on fetal malposition [34, 35, 36]. Balchin et al. [36] reported the strongest association for vaginal breech delivery (AOR = 4.71, 95% CI: 4.16–5.33). Tantu et al. [35] found an AOR of 2.640 (95% CI: 1.002–6.950) for cephalopelvic disproportion. Asaye et al. [34] reported an AOR of 1.89 (95% CI: 1.14–3.16).

3.10.3. Domain III: Maternal Factors

3.10.3.1. Hypertensive Disorders of Pregnancy

Eight studies reported on hypertensive disorders [16, 34, 35, 37, 43, 46, 47, 48]. Tantu et al. [35] reported that eclampsia was associated with 8.0 times higher odds (AOR = 8.022, 95% CI: 1.634–39.372). Hailemariam et al. [46] found the strongest association for preeclampsia (AOR = 5.498, 95% CI: 1.579–19.145). Beyene et al. [48] reported an AOR of 5.08 (95% CI: 2.76–9.35) for pregnancy‐induced hypertension. Addisu et al. [43] reported an AOR of 3.45 (95% CI: 1.26–9.37). Abate et al. [37] and Asaye et al. [34] reported AORs of 2.43 and 2.10, respectively. Tolu et al. [16] found that 49.1% of MSAF cases had pregnancy‐induced hypertension compared with 35.5% of controls.

3.10.3.2. Diabetes Mellitus

Four studies examined the association with diabetes [33, 51, 52]. Sarwar et al. [33] reported a significant association for gestational diabetes mellitus (p < 0.001; 41% in MSAF). Itzhaki‐Bachar et al. [51] found that both pregestational diabetes (3.5% vs. 1.5%, p = 0.024) and gestational diabetes (17.9% vs. 14.7%, p = 0.049) were associated with MSAF. Shekari et al. [52] found no significant association after adjustment (AOR = 0.79, 95% CI: 0.33–0.91).

3.10.3.3. Anemia

Five studies reported on anemia [33, 37, 45, 50, 53]. Tefera et al. [45] found that a normal hematocrit level was protective (AOR = 0.17, 95% CI: 0.07–0.4). Sarwar et al. [33] reported that anemia was significantly associated with meconium aspiration syndrome (p < 0.001). Abate et al. [37] found no significant association (AOR = 1.37, 95% CI: 0.66–2.84). Descriptive studies reported anemia in 6.4% to 28.2% of MSAF cases [50, 53]. The protective effect of anemia is paradoxical and may reflect residual confounding; non‐significant findings in other studies support the need for higher‐quality research.

3.10.3.4. Inflammatory Conditions and Intrauterine Infection

Four studies reported on inflammatory conditions [36, 41, 51, 54]. Murata et al. [54] found that intrauterine infection was more common in the MSAF group (3.2% vs. 0.5%, p < 0.001). Itzhaki‐Bachar et al. [51] reported that intrahepatic cholestasis of pregnancy was more common in the thick MSAF group (3.2% vs. 0.5%, p = 0.035). Balchin et al. [36] found that maternal pyrexia was associated with MSAF (AOR = 1.62, 95% CI: 1.50–1.74). Osava et al. [41] noted an association with chorioamnionitis in the discussion.

3.10.3.5. Antepartum Hemorrhage

Three studies reported on antepartum hemorrhage [7, 35, 49]. Dereje et al. [49] reported the strongest association (AOR = 8.43, 95% CI: 2.02–35.17). Tantu et al. [35] reported that 3.2% of MSAF cases had antepartum hemorrhage, and Karpe et al. [7] reported 0.5%.

3.10.4. Domain IV: Fetal and Physiological Factors

3.10.4.1. Advanced Gestational Age

Advanced gestational age was the most consistently reported factor, identified in 14 studies [35, 36, 37, 38, 39, 41, 42, 43, 45, 49, 50, 52, 53, 55]. Dereje et al. [49] reported the strongest association for late‐term pregnancy (41–41⁺⁶ weeks) with an AOR of 8.82 (95% CI: 3.18–24.49). Shekari et al. [52] found AORs of 5.12 (95% CI: 2.76–8.94) for 40⁺¹–41 weeks and 7.09 (95% CI: 3.92–9.80) for gestations exceeding 41 weeks. Balchin et al. [36] reported a 39% increase in MSAF risk per additional week of gestation (AOR = 1.39, 95% CI: 1.38–1.40). Oyelese et al. [55] demonstrated a steady increase in MSAF incidence from 1.2% at 32 weeks to 100% at 42 weeks. David et al. [42] found no MSAF cases before 37 weeks but 31.3% at 42 weeks or more (p = 0.001).

3.10.4.2. Primiparity/Nulliparity

Nine studies examined primiparity as a risk factor [16, 34, 35, 36, 37, 41, 42, 50, 53]. Tantu et al. [35] reported the strongest association (AOR = 3.643, 95% CI: 1.215–10.921). Asaye et al. [34] found an AOR of 2.48 (95% CI: 1.63–3.79). Osava et al. [41] reported a prevalence ratio of 1.49 (95% CI: 1.29–1.73). Descriptive studies showed that 50.5% to 62.9% of MSAF cases occurred in primigravida women [50, 53]. Abate et al. [37] did not find a significant association (AOR = 0.62, 95% CI: 0.34–1.11).

3.10.4.3. Maternal Age

Four studies examined maternal age [36, 41, 43, 52]. Addisu et al. [43] reported that maternal age exceeding 30 years was associated with 5.6 times higher odds of MSAF (AOR = 5.63, 95% CI: 3.35–9.44). Shekari et al. [52] found that adolescent mothers (13–19 years) had 3.1 times higher odds (AOR = 3.07, 95% CI: 1.87–4.98). Balchin et al. [36] reported an AOR of 1.26 (95% CI: 1.18–1.36) for maternal age of 40 years or older. Osava et al. [41] found no significant association.

3.10.4.4. Fetal Sex (Male)

Two studies reported an association between male fetal sex and MSAF [36, 54]. Balchin et al. [36] found a modest association (AOR = 1.13, 95% CI: 1.11–1.15). Murata et al. [54] reported that 57.5% of MSAF cases were male compared with 51.4% in controls (p < 0.001).

3.10.4.5. Birth Weight/Macrosomia

Three studies reported on birth weight [36, 41, 51]. Itzhaki‐Bachar et al. [51] found that macrosomia (birth weight exceeding 4000 g) was significantly more common in the MSAF group (14.9% vs. 5.8%, p < 0.001). Osava et al. [41] reported a prevalence ratio of 1.47 for birth weight of 4000 grams or more. Balchin et al. [36] reported an AOR of 1.20 for birth weight at or above the 90th percentile.

3.10.4.6. Intrauterine Growth Restriction (IUGR)

Four studies examined IUGR [37, 43, 49, 53]. None of the studies reporting adjusted odds ratios found a statistically significant association [37, 43, 49]. Dereje et al. [49] reported an AOR of 3.04 (95% CI: 0.74–12.50), Addisu et al. [43] reported AOR of 2.4 (95% CI: 0.775–7.70), and Abate et al. [37] reported an AOR of 2.54 (95% CI: 0.88–7.29). Patel et al. [53] reported that 4.95% of MSAF cases had IUGR without a statistical analysis. No adjusted analysis for IUGR reached statistical significance; the current evidence is insufficient to confirm IUGR as a risk factor for MSAF.

4. Discussion

This comprehensive meta‐analysis, encompassing 44 studies and 1,414,705 births globally, estimates the pooled prevalence of MSAF at 13.0% (95% prediction interval: 6.9%–23.1%), indicating that approximately one in eight pregnancies is affected. This prevalence substantiates MSAF as a relatively common intrapartum finding requiring vigilant clinical management [56]. The exceptionally high heterogeneity (I ² = 99.71%) observed underscores substantial variation across populations, which we systematically explored through subgroup analyses, meta‐regression, and prediction intervals. Recent methodological evidence confirms that extreme heterogeneity is typical in prevalence meta‐analyses, reflecting real epidemiological variation rather than methodological inadequacy [57, 58].

The most clinically consequential finding of this study is the pronounced disparity in MSAF prevalence across geographical and socioeconomic strata. Prevalence in low‐income countries (22.2%) was approximately double that in high‐income nations (11.1%) (p < 0.001). This global gradient is reinforced by national‐level evidence from Ethiopia, where two recent independent systematic reviews reported remarkably consistent pooled prevalence estimates of 20.0% [19] and 19.58% [18], aligning precisely with our estimate for this income category. To our knowledge, these two regional reviews [18, 19] are the only systematic reviews and meta‐analyses that have specifically examined the prevalence and determinants of MSAF. Both were conducted exclusively in Ethiopia and reported regional estimates substantially higher than our global pooled prevalence, reflecting the disproportionate burden of MSAF in sub‐Saharan Africa. The determinants identified in these reviews—including pregnancy‐induced hypertension, premature rupture of membranes, and obstructed labor—are consistent with our descriptive synthesis, confirming the robustness of these associations across different settings. However, no previous global systematic review or meta‐analysis has quantified MSAF prevalence across different income levels and continents or synthesized modifiable health‐system factors such as inadequate antenatal care and delayed referral. This global‐regional comparison underscores the novelty of our study and highlights the need for context‐specific interventions. This disparity likely reflects systemic factors—including differential access to quality antenatal care, higher burden of untreated maternal comorbidities, and suboptimal intrapartum monitoring [59, 60]—which are modifiable through targeted health system strengthening.

The doubling of MSAF prevalence in low‐income countries (22.2% vs. 11.1%) suggests that clinicians in resource‐limited settings should maintain a lower threshold for suspecting fetal distress, while health systems should prioritize neonatal resuscitation preparedness and timely referral pathways. Among the four domains identified, Social and Structural Factors—particularly inadequate antenatal care, delayed referral, and low income—reinforce the need to strengthen antenatal coverage and address socioeconomic barriers [51, 61]. Intrapartum Factors—including prolonged labor, obstructed labor, and PROM—underscore the importance of partograph‐based monitoring and timely obstetric interventions [17, 37, 42]. The significant association between meconium consistency and prevalence (p = 0.004) supports adoption of a standardized three‐grade classification system for risk stratification. Collectively, these findings shift the focus from established risk factors to actionable health system improvements, aligning with the United Nations Sustainable Development Goals (SDG 3 and SDG 10) by targeting preventable causes of perinatal morbidity and reducing global disparities.

Our analysis revealed a distinct prevalence pattern for meconium consistency: moderate (Grade II) meconium was most common (5.7%), followed by thin (Grade I: 4.7%), with thick (Grade III) being the least prevalent (3.0%) (p = 0.004). Despite its lower prevalence, thick meconium carries the greatest perinatal risk. Evidence links thick MSAF to significantly higher rates of abnormal fetal heart rate patterns, operative deliveries for fetal compromise, and poor neonatal outcomes [13, 62]. A cohort study demonstrated a dose‐dependent increase in adverse neonatal outcomes, reporting adjusted odds ratios of 16.8 for Grade II and 33.8 for Grade III MSAF compared to clear fluid [63]. A critical caveat is the substantial heterogeneity in grading methods across included studies; only a minority employed the standard three‐grade system [2], while many used binary classifications or provided no grading at all. Therefore, we recommend that all delivery units adopt a standardized three‐grade classification system, as this simple, low‐cost stratification can meaningfully guide intrapartum decision‐making regarding the intensity of fetal monitoring and preparedness for neonatal resuscitation.

Meta‐regression identified increasing mean gestational age as a significant independent predictor of MSAF, reflecting a well‐established physiological relationship linked to fetal gastrointestinal maturation and rising uteroplacental insufficiency as pregnancy advances [64]. This finding aligns with previous regional reviews identifying post‐term pregnancy as a key determinant [19].

Classification of the 22 identified risk factors into four domains—Social/Structural, Intrapartum, Maternal, and Fetal/Physiological—reveals that the strongest modifiable determinants are intrapartum: NRFHRP (AOR up to 21.9), obstructed labor (AOR up to 24.6), and prolonged labor (AOR up to 7.5), reflecting failures in labor monitoring and timely decision‐making. System‐level barriers—delayed referral (AOR up to 15.3), inadequate ANC, and low income—reinforce MSAF as both a clinical and health system problem. Among maternal factors, hypertensive disorders (AOR up to 8.0) were most significant, supporting antenatal screening and blood pressure control. Advanced gestational age (AOR up to 8.8) was the strongest biological driver, suggesting induction at 41 weeks may reduce risk. IUGR showed no significant association, with insufficient evidence to confirm it as a risk factor. This framework shifts focus from biological description to actionable targets for policy and practice.

4.1. Implications for Future Research

Several research priorities emerge from our findings. Prospective cohort studies with standardized MSAF definitions and three‐grade classification systems are needed to better establish causal pathways and validate risk stratification approaches. Implementation research should evaluate whether routine meconium grading, when introduced into clinical practice, actually improves neonatal outcomes. Qualitative research exploring barriers to timely intrapartum care in high‐prevalence, low‐income settings may identify modifiable health system bottlenecks. Finally, country‐specific prevalence studies are urgently needed in nations currently represented by single‐study estimates to confirm or refine our preliminary figures.

4.2. Limitations

Several limitations should be acknowledged. Despite extensive subgroup analyses and meta‐regression, substantial heterogeneity (I ² = 99.71%) remained, reflecting genuine differences in populations, healthcare settings, and diagnostic practices. The prediction interval (6.9%–23.1%) was therefore reported to provide a clinically relevant range for individual settings. Due to high heterogeneity among risk factor studies, we refrained from pooling and presented a descriptive synthesis, which precludes causal inference. Variations in MSAF diagnostic criteria, grading systems, and labor management protocols across studies may have influenced prevalence estimates. Furthermore, the diagnosis and grading of meconium thickness rely on visual inspection, which is inherently subjective and subject to inter‐observer variability among healthcare providers, potentially influencing the reported prevalence estimates across studies. We acknowledge that observational studies on intrapartum events are prone to reporting bias. However, our sensitivity analysis excluding moderate‐quality studies confirmed the robustness of the pooled estimate. Additionally, the generalizability of findings to settings with different healthcare infrastructures may be limited, as most studies were conducted in hospital‐based populations.

5. Conclusion

This meta‐analysis establishes a pooled global prevalence of MSAF at 13.0% with a 95% prediction interval ranging from 6.9% to 23.1%, demonstrating substantial variation by country, continent, and income level. The most clinically actionable finding is the doubling of prevalence in low‐income countries compared to high‐income nations, which should inform resource allocation and clinical preparedness strategies. Meconium consistency grading, particularly the identification of thick meconium, offers a simple and low‐cost tool for risk stratification. Among 22 risk factors classified into four domains, the strongest actionable targets are system‐level: reducing referral delays, improving labor monitoring, managing hypertensive disorders, and inducing post‐term pregnancies. IUGR currently lacks sufficient evidence to be confirmed as a risk factor. Addressing modifiable system factors and structural inequities can reduce perinatal morbidity, particularly in resource‐limited settings where the burden is highest.

Author Contributions

Shervin Tabrizian: conceptualization, investigation, supervision, writing – review and editing, funding acquisition. Tiba Mirzarahimi: conceptualization, methodology, supervision, writing – review and editing. Mojgan Mirghafourvand: conceptualization, investigation, software, formal analysis. Mahsan Nabighadim: conceptualization, investigation, methodology, software, writing – original draft.

Ethics Statement

This study was approved by the Ethics Committee of Ardabil University of Medical Sciences, with the code IR.ARUMS.MEDICINE.REC.1404.094. This study is a systematic review and meta‐analysis of previously published data and does not involve direct human or animal participation.

Conflicts of Interest

The authors declare no conflicts of interest.

Transparency Statement

Mahsan Nabighadim affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

Supporting information

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Data Availability Statement

Data derived from the original published studies.