Association of short interpregnancy interval with low birth weight and preterm birth in Ethiopia: a systematic review and meta-analysis

Abstract

Objectives

Evidence from developing countries showed that short interpregnancy intervals are associated with low birth weight (LBW) and preterm birth (PB). However, in Ethiopia, the association between short birth intervals and LBW and PB remains inconclusive. Therefore, this review aimed to provide a comprehensive nationwide estimate of the association between short interpregnancy intervals and LBW and PB in Ethiopia.

Design

A systematic review and meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

Data sources

PubMed/Medline, EMBASE, Web of Science, Cochrane library, Google Scholar and institutional repositories were searched to retrieve relevant articles.

Eligibility criteria

All observational studies conducted in Ethiopia that reported the association between short interpregnancy intervals and LBW, PB or both were included. Studies were excluded if they were animal studies, case reports, conference abstracts or had insufficient data to compute the required effect estimates.

Data extraction and synthesis

Two independent reviewers extracted the data using a standardised data extraction form. Stata V.14 was used for data analysis. A random-effects model was applied to estimate the pooled association between short interpregnancy interval and LBW and PB, with 95% CIs.

Results

Women with a short interpregnancy interval had 1.34 times higher odds of delivering an LBW infant (OR=1.34; 95% CI: 1.14 to 1.58) and 1.56 times higher odds of PB (OR=1.56; 95% CI: 1.27 to 1.92) compared with women with an optimal birth interval.

Conclusions

Short interpregnancy interval was associated with an increased risk of LBW and PB. Therefore, community- and facility-based interventions promoting optimal birth spacing, alongside universal access to family planning services—including modern contraceptive methods and breastfeeding promotion—are recommended.

WHAT IS ALREADY KNOWN ON THIS TOPIC

• Evidence from developing countries shows that short interpregnancy intervals are associated with adverse birth outcomes, particularly low birth weight (LBW) and preterm birth (PB).

• In Ethiopia, findings on the relationship between short birth intervals and adverse neonatal outcomes have been inconsistent and fragmented across individual studies.

WHAT THIS STUDY ADDS

• This study provides a nationwide estimate in Ethiopia quantifying the effect of short interpregnancy interval on LBW and PB.

• The findings strengthen the evidence base by synthesising data from 15 observational studies using robust meta-analytical methods.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• The findings support strengthening community-based and facility-based birth spacing interventions and underscore the need to scale up universal access to modern family planning services and promote optimal breastfeeding practices in Ethiopia to reduce preventable adverse birth outcomes.

Introduction

Globally, a short interpregnancy interval is the time between two births, significantly associated with different adverse maternal and perinatal outcomes.¹ The WHO recommended a pregnancy interval of at least 24 months, which corresponds to 33 months of birth-to-birth interval.² Those pregnancies that occurred within 24 months of the preceding are considered high risk pregnancies, which are associated with a high risk of complications.³ This increased risk of complication during pregnancy and delivery associated with short birth intervals (SBIs) is significantly higher in low- and middle-income countries, particularly in Africa, including Ethiopia.⁴

SBIs are associated with a range of adverse neonatal outcomes, including low birth weight (LBW), preterm birth (PB), intrauterine growth restriction, small for gestational age, stillbirth and neonatal mortality.^5,6 Evidence indicates that an SBI has a significant association with LBW and PB.^1,7 For example, a study done in Sudan showed that those reproductive-aged women with SBIs had almost two times the increased risk of LBW and PB.⁵ Another study conducted in Tanzania revealed that SBIs were associated with LBW (1.6 times) and PB (1.5 times).⁶ Furthermore, SBIs also increased the risk of infant mortality. Evidence revealed that the risk of infant mortality was increased by 50% with SBIs.⁸ The risk of neonatal and infant mortality decreases with increasing birth interval lengths up to 36 months, at which point the risk plateaus.⁴ In Ethiopia, nearly half of reproductive-aged women gave birth within a period of 24 months from the preceding birth.⁹

Globally, LBW and PB are the two most common direct causes of neonatal morbidity and mortality, especially in low- and middle-income countries.¹⁰ Neonates born as preterm or LBW are at higher risk of stillbirth and neonatal death and also have increased health and developmental risks throughout their lifetime, such as under-five death and non-communicable diseases (diabetes and cardiovascular risks).¹¹ Of the 2.5 million neonatal deaths occurring globally, more than 90% were reported in low-income countries, with approximately 80% attributable to LBW and PB, including one-third due to PB and one-third due to LBW.¹² In Ethiopia, despite a continuous decline in under-five mortality, neonatal mortality has remained persistent and even increased from 29 deaths per 1000 live births in 2016 to 30 deaths per 1000 live births in 2019.¹³ Prematurity, sepsis and LBW are the primary causes of neonatal mortality in the country.^14,15

Evidence and studies have confirmed that SBIs significantly influence and contribute to LBW and PB, which are responsible for the unacceptably high burden of neonatal mortality.^16–22 However, none of the studies have shown the pooled effect of SBIs on LBW and PB in Ethiopia. This indicates that there is a strong need to systematically review available evidence on the association of short interpregnancy intervals with LBW and PB in Ethiopia. Therefore, estimating the pooled association between short interpregnancy intervals and LBW and PB in Ethiopia will provide critical insights for policymakers and practitioners aimed at reducing neonatal morbidity and mortality.

Methods

Design, data sources and searching strategies

Electronic databases, including PubMed/Medline, EMBASE, Web of Science, Cochrane Library, Google Scholar and institutional repositories, were systematically searched to identify published articles examining the association between short interpregnancy intervals and perinatal outcomes, including LBW and PB. Keywords such as interpregnancy interval, SBI, adverse birth outcomes, adverse neonatal outcomes, LBW, PB and Ethiopia, along with relevant Medical Subject Headings (MeSH) terms, were combined using Boolean operators (OR and AND) to retrieve pertinent articles (online supplemental file 1). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to report this review²³ (online supplemental file 2). An independent literature search was conducted up to 20 February 2026.

Eligibility criteria

Inclusion criteria

All observational studies, primarily case-control and cross-sectional designs, conducted across all regional states and administrative cities of Ethiopia up to February 2026, and reporting the association between short interpregnancy intervals and LBW, PB or both, published solely in English, were included in this meta-analysis. No restrictions were applied regarding publication status, year of publication or sampling technique.

Exclusion criteria

Animal studies, case reports, conference abstracts and studies lacking sufficient data to compute key variables were excluded in the final analysis. Additionally, papers that were not fully accessible during the search process were excluded after at least two attempts to contact the principal investigator via email. Furthermore, studies deemed to be of poor quality based on established review criteria were excluded from the final analysis.

Outcomes and exposures

Exposure

The exposure examined in this review was a short interpregnancy interval. A short interpregnancy interval is defined as an interval of less than 24 months between the date of a live birth and the conception of the subsequent pregnancy. In contrast, an optimal interpregnancy interval is considered to be 24 months or more between the date of live birth and the conception of the subsequent pregnancy.^24–26

Outcome variables

The primary outcomes of this review are PB and LBW. PB is defined as the birth of a neonate before 37 completed weeks of gestation.^27–29 Gestational age was determined using the last menstrual period, early ultrasound assessment or the Ballard maturity examination. LBW was defined as a birth weight of less than 2500 g, measured within the first hour after birth, regardless of gestational age.^17–19,30

Data extraction

Data extraction was conducted using the 2014 Joanna Briggs Institute Reviewers’ standardised data extraction format, recorded in an Excel spreadsheet.³¹ Reviewers systematically extracted information including the primary study author’s name, study location, publication year, study design and methodology and sample size. Additionally, unadjusted ORs, representing associations between the outcome variable and exposure, were extracted through cross-tabulation. Any discrepancies among the authors were resolved through face-to-face discussions and consensus.

Quality assessment

We evaluated the primary studies’ methodological quality and risk of bias using the Newcastle-Ottawa Scale (NOS) developed by Hoy et al.³² The NOS has the following appraisal criteria: (1) representation, (2) sampling, (3) random selection, (4) non-response bias, (5) data collection, (6) case definition, (7) reliability and validity of study tool, (8) method of data collection, (9) prevalence period and (10) numerator and denominator. The rating scale categorised as low risk of bias (‘yes’ answers to domain questions) or high risk of bias (‘no’ answers to domain questions) for each article. Each study was assigned a score of 1 (Yes) or 0 (No) for each domain, and these scores were summed to provide an overall study quality score. Scores of 8–10 were considered as having a ‘low risk of bias’, 6–7 a ‘moderate risk’ and 0–5 a ‘high risk’. For the final risk of bias classification, disagreements between the reviewers were resolved via consensus.

Certainty of evidence

The level of evidence for each outcome was evaluated using the approach recommended by the Grading of Recommendations Assessment, Development and Evaluation (GRADE) Working Group. Observational studies were initially rated as low certainty and were subsequently downgraded or upgraded based on the following domains: risk of bias, inconsistency, indirectness, imprecision and publication bias.

Data analysis

First the extracted data were computed in Excel spreadsheet and then imported to Stata V.17 for further analysis. Cochran’s Q statistics with inverse variance (I²) was used to assess the existence of statistical heterogeneity. Low, moderate and high heterogeneity were considered at 25%, 50% and 75%, respectively. In addition, p value less than 0.05 was used to confirm the presence of heterogeneity across studies.³³ A pooled effect estimate was calculated to synthesise evidence across studies examining the association between short interpregnancy interval and LBW and PB in Ethiopia. Although the included studies were conducted across five regional states and varied in sample size, they addressed a comparable research question using similar operational definitions and measurement approaches. Given the relatively small sample sizes of primary studies and the anticipation of between-study variability arising from differences in geographical region, socio-cultural context and urban–rural composition, a random-effects model (DerSimonian and Laird method) was employed. This approach assumes that the true effect size may vary across studies and provides a more conservative estimate by incorporating both within-study and between-study variance. The use of a random-effects pooled estimate was therefore considered appropriate to generate a summary measure while accounting for contextual and methodological diversity across studies. A forest plot diagram was used to describe the association between exposure and outcomes, such as LBW and PB.

Patient and public involvement

Since a systematic review and meta-analysis study, patient and public involvement were not applicable.

Results

Original study selection process and explanations

A total of 1457 articles were identified through searches of health-related and medical-related electronic databases and other sources. Of these, 853 articles were excluded as duplicates. Following this, 604 publications were screened, resulting in the removal of 469 articles due to irrelevant titles. Subsequently, 135 articles were assessed against eligibility criteria. After this evaluation, 115 articles were excluded as a result of not reporting the specific outcomes of interest, exposures and/or poor quality. Ultimately, 20 studies met the eligibility criteria and were included in this review. Among these, 12 studies examined the association between short interpregnancy intervals and LBW, while eight studies analysed the association between short interpregnancy intervals and PB in Ethiopia (figure 1).

Figure 1: PRISMA. flow diagram of included studies to estimate the pooled association of short interpregnancy intervals and perinatal outcomes, LBW and PB in Ethiopia. LBW, low birth weight; NOS, Newcastle-Ottawa Scale; PB, preterm birth; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

Characteristics of the included primary studies

Regarding publication status, all of the included articles were published across reputable journals. 13 of the included studies employed a case–control study methodology, three of them were cohort and the remaining four were cross-sectional. The studies were conducted in Ethiopia, with sample sizes ranging from 264 to 2371 participants, with a total of 10 102 reproductive-aged women included in this meta-analysis. Among the included studies, five articles originated from the Southern Nations, Nationalities and Peoples (SNNP) region,^{17,20,28,34,35} four from Amhara,^16,19,21,36 four from Tigray,^25,27,37,38 four from Oromia,^18,22,39,40 one from Southern Ethiopia⁴¹ and one from Harari.⁴² Using the NOS quality assessment tool, each individual article scored between 6 and 9 out of 10 (table 1). In terms of risk of bias assessment, based on the tool developed by Hoy et al, 12 studies (60%) were classified as having a low risk of bias, while 8 studies (40%) were deemed to have a moderate risk of bias (online supplemental file 3). Four studies scoring below 5 out of 10 on the NOS were excluded from the meta-analysis due to high risk of bias, in accordance with our predefined eligibility criteria (online supplemental file 4). To evaluate the impact of studies with moderate risk of bias on the pooled effect size estimates, analyses were conducted excluding these studies. The CIs for the pooled effect size, with and without the moderate risk studies, overlapped, indicating no significant difference. All included studies reported a positive association between short interpregnancy intervals and adverse perinatal outcomes, such as LBW and PB, although the strength of the association varied.

Table 1. Descriptive summary of studies included in the meta-analysis of the association of short interpregnancy interval and LBW and PB in Ethiopia.

Author name	Study year	Region	Study design	Sampling technique	Variable	Sample size	NOS score
Aregawi et al37	2019	Tigray	Cross-sectional	Systematic	PB	472	8
Abaraya et al.22	2018	Oromia	Case–control	Simple random	PB	656	6
Fetene et al.28	2022	SNNP	Case–control	Consecutive	PB	405	7
Brhane et al38	2019	Tigray	Cohort	Systematic	PB	480	9
Woday et al.36	2019	Amhara	Case–control	Consecutive	PB	417	7
Zewde42	2020	Harari	Cross-sectional	Systematic	PB	325	8
Teklay et al27	2018	Tigray	Case–control	Systematic	PB	264	9
Mekuriyaw et al21	2020	Amhara	Case–control	Systematic	PB	405	7
Gurmu et al26	2022	Benishangul-Gumz	Cohort	Systematic	LBW	438	8
Jena et al41	2022	South Ethiopia	Cohort	Convenient	LBW	2371	7
Yesuf et al16	2016	Amhara	Case–control	Consecutive	LBW	453	8
Mingude et al34	2020	SNNP	Case–control	Consecutive	LBW	300	9
Desta et al25	2020	Tigray	Case–control	Systematic	LBW	381	9
Deriba and Jemal39	2021	Oromia	Case–control	Systematic	LBW	555	8
Bekela et al17	2020	SNNP	Case–control	Consecutive	LBW	354	8
Jember et al19	2020	Amhara	Cross-sectional	Systematic	LBW	358	9
Egata and Bafa20	2019	SNNP	Case–control	Consecutive	LBW	270	6
Demelash et al18	2015	Oromia	Case–control	Consecutive	LBW	387	7
Alemu et al35	2019	SNNP	Cross-sectional	Systematic	LBW	341	8
Gizaw and Gebremedhin40	2018	Oromia	Case–control	Convenient	LBW	470	7

LBW, low birth weight; NOS, Newcastle-Ottawa Scale; PB, preterm birth; SNNP, Southern Nations, Nationalities and Peoples.

Publication bias

Visual inspection of the funnel plot indicated a relatively symmetrical distribution of studies around the pooled effect estimate, suggesting the absence of substantial publication bias (figure 2). This observation was further supported by statistical tests of funnel plot asymmetry. Egger’s regression test revealed no significant evidence of publication bias (p=0.079), and Begg’s rank correlation test also indicated no statistically significant small-study effects (p=0.115). Therefore, there was no strong evidence of publication bias among the included studies.

Figure 2. Funnel plot.

Meta-analysis

The association between short interpregnancy interval and PB in Ethiopia

According to the pooled analysis of eight primary studies^{21,22,27,28,36–38,42}, the odds of PB among women who had short interpregnancy intervals were 1.56 times higher when compared with women with interpregnancy intervals ≥24 months (OR=1.56; 95% CI 1.27 to 1.92) (figure 3). As it was indicated, the presence of a substantial level of heterogeneity (I²=56.8% at p-value <0.001) across included studies made the use of a random-effects model for analysis appropriate.

Figure 3. Forest plots which describe the association between short interpregnancy interval and preterm birth in Ethiopia.

The association between short interpregnancy interval and LBW in Ethiopia

The second objective of this meta-analysis was to investigate the association between SBI and LBW. 12 primary studies^{16–20,25,26,34,35,39–41} were included to assess the association between short interpregnancy intervals and LBW, revealing a significant association. The analysis indicated that the odds of LBW were 1.34 times higher among women with short interpregnancy intervals compared with those with intervals of ≥24 months (OR=1.34; 95% CI 1.14 to 1.58). A low level of heterogeneity was observed among the included studies, as indicated by an I² value of 12.6% and a p value of <0.001 (figure 4).

Figure 4. Forest plots showing the association between short interpregnancy interval and LBW in Ethiopia. LBW, low birth weight.

Subgroup analysis

Subgroup analysis by region showed variability in the association between SBI and PB. In Amhara (OR=1.550; 95% CI 0.975 to 2.466), Harari (OR=1.191; 95% CI 0.707 to 2.007) and SNNP (OR=1.646; 95% CI 0.874 to 3.100), the associations were positive but not statistically significant. In contrast, a statistically significant association was observed in Oromia (OR=1.429; 95% CI 1.021 to 2.001), and this study contributed the largest weight to the pooled estimate. The strongest association was found in Tigray (OR=2.437; 95% CI 1.466 to 4.052), indicating more than a twofold increase in the odds of PB among women with short interpregnancy interval (table 2).

Table 2. A subgroup analysis of the association between short interpregnancy interval and preterm birth in Ethiopia.

Study	OR	95% CI	Weight %
Amhara
Woday et al36	1.449	0.754 to 2.784	9.97
Mekuriyaw et al21	1.661	0.858 to 3.215	9.76
Exp.	1.550	0.975 to 2.466
Harari
Zewde42	1.191	0.707 to 2.007	15.64
Exp.	1.191	0.707 to 2.007
Oromia
Abaraya M et al22	1.429	1.021 to 2.001	37.57
Exp.	1.429	1.021 to 2.001
SNNP
Fetene et al28	1.646	0.874 to 3.100	10.62
Exp.	1.646	0.874 to 3.100
Tigray
Aregawi et al.37	2.570	1.179 to 5.601	7.00
Brhane et al38	2.885	1.354 to 6.146	7.43
Teklay et al27	1.085	0.253 to 4.648	2.01
Exp.	2.437	1.466 to 4.052
Overall
Exp.	1.564	1.273 to 1.923

SNNP, Southern Nations, Nationalities and Peoples.

Similarly, regional subgroup analysis for the association between short interpregnancy interval and LBW revealed predominantly positive but heterogeneous estimates. In Amhara, pooling two studies yielded an OR of 1.469 (95% CI 0.940 to 2.294), reflecting a positive yet statistically non-significant association. In Benishangul-Gumuz, the single included study reported a comparable non-significant estimate (OR=1.431; 95% CI 0.738 to 2.775). In Oromia, three studies demonstrated a statistically significant association between SBI and LBW (OR=1.434; 95% CI 1.034 to 1.988). In SNNP, four studies produced a pooled OR of 1.306 (95% CI 0.969 to 1.761), which did not achieve statistical significance. Likewise, in Southern Ethiopia (OR=1.311; 95% CI 0.858 to 2.002) and Tigray (OR=1.105; 95% CI 0.686 to 1.781), the associations remained positive but non-significant (table 3).

Table 3. A subgroup analysis of the association between short interpregnancy interval and low birth weight in Ethiopia.

Study	OR	95% CI	Weight %
Amhara
Yesuf et al16	1.488	0.835 to 2.652	7.91
Jember et al19	1.441	0.715 to 2.905	5.38
Exp.	1.469	0.940 to 2.294
Benishangul-Gumez
Gurmu et al26	1.431	0.738 to 2.775	6.02
Exp.	1.431	0.738 to 2.775
Oromia
Deriba and Jemal39	1.131	0.684 to 1.868	10.49
Demelash et al18	1.579	0.870 to 2.868	7.42
Gizaw and Gebremedhin40	1.860	0.999 to 3.463	6.84
Exp.	1.434	1.034 to 1.988
SNNP
Mingude et al34	1.592	0.715 to 3.542	4.13
Bekela et al17	1.104	0.584 to 2.087	6.52
Egata and Bafa20	1.252	0.769 to 2.036	11.16
Alemu et al35	1.440	0.804 to 2.579	7.78
Exp.	1.306	0.969 to 1.761
Southern Ethiopia
Jena et al41	1.311	0.858 to 2.002	14.73
Exp.	1.311	0.858 to 2.002
Tigray
Desta et al25	1.105	0.686 to 1.781	11.60
Exp.	1.105	0.686 to 1.781
Overall
Exp.	1.340	1.139 to 1.576

SNNP, Southern Nations, Nationalities and Peoples.

Certainty of evidence

According to GRADE assessment, the certainty of evidence for the association between SBI and LBW was rated as low. The pooled analysis showed low heterogeneity (I²=12.6%, p<0.001), suggesting consistent findings across studies. No serious concerns regarding risk of bias, indirectness or imprecision were identified. Furthermore, assessment of publication bias using funnel plot symmetry and statistical tests showed no evidence of publication bias. In contrast, the certainty of evidence for the association with PB was rated as moderate. Substantial heterogeneity was observed (I²=56.8%, p<0.001), reflecting inconsistency in effect estimates among studies. Assessment of publication bias using funnel plot symmetry and statistical tests indicated no evidence of publication bias, and the included studies were judged to have low risk of bias. A detailed GRADE assessment for all outcomes is provided (online supplemental file 5).

Discussion

This meta-analysis aimed to investigate the association between short interpregnancy intervals with birth outcomes, specifically PB and LBW. The interval between successive pregnancies is a modifiable risk factor influencing various adverse birth outcomes that contribute significantly to neonatal morbidity and mortality. To mitigate this risk, the WHO recommends an interval of at least 2 years following a live birth.²

Accordingly, this review identified a significant association between short interpregnancy intervals and both PB and LBW. The odds of PB among women with short interpregnancy intervals were 1.34 times higher compared with women with short interpregnancy intervals ≥24 months. This finding is supported by a retrospective study conducted in Tanzania, which identified a short interpregnancy interval as an independent risk factor that doubles the risk of PB.⁶ Furthermore, meta-analytical evidence indicates that interpregnancy intervals shorter than 18 months increased the risk of PB.⁴³ A longitudinal cohort study in Israel revealed that intervals shorter than 6 months significantly elevate the risk of PB.⁴⁴ Additionally, evidence from the USA and a study in Portugal similarly reported that short interpregnancy intervals substantially increased the risk of PB.^45,46

Another key finding of this meta-analysis is that SBIs were associated with a 1.56-fold increased risk of LBW. This finding is consistent with evidence from Sudan and sub-Saharan Africa, which indicates that an interpregnancy interval shorter than 18 months is independently and significantly associated with an increased risk of adverse perinatal outcomes, particularly LBW and PB.^5,47 Additionally, studies conducted in Qatar and the USA reported that an SBI, specifically less than 12 months, significantly increases the risk of LBW.^1,48 Furthermore, studies from Poland and Nepal support our finding, indicating that the risks of LBW are more than doubled among women with SBIs.^49,50 Moreover, this finding aligns with a study in the USA which showed that mothers with intervals of less than 6 months have an approximately 50–80% increased risk of very LBW.⁵¹

Several hypotheses have been proposed to elucidate the association between adverse birth outcomes and SBIs, particularly PB and LBW. SBIs do not provide sufficient time for maternal recovery from the nutritional depletion and physiological stress of the preceding pregnancy, which is crucial for the growth and development of subsequent pregnancies.⁵² Consequently, maternal depletion syndrome results in a less favourable intrauterine environment for the subsequent pregnancy, representing a key underlying factor for adverse birth outcomes.³ Inadequate maternal nutritional replenishment, coupled with increased folate requirements during pregnancy, contributes to anaemic and other nutritional disorders, which are implicated in various adverse perinatal outcomes, including PB and LBW perinatal outcomes including PB and LBW.^3,53 Another frequently cited hypothesis regarding SBIs concerns sibling competition, whereby limited familial resources may be preferentially allocated to the first born, leaving subsequent offspring with an insufficient share, particularly in low-income settings such as Ethiopia.^2,3

Although the magnitude of the association between short interpregnancy interval and PB varied across regions, the direction of effect was consistently positive. The strongest association observed in Tigray may reflect regional differences in maternal healthcare access and quality, socio-economic conditions or study-level characteristics. The non-significant findings in certain regions are likely due to limited sample size, reduced statistical power and imprecision rather than absence of effect.

Similarly, for LBW, the direction of association with short interpregnancy interval was uniformly positive across regions; however, statistical significance was observed only in Oromia. The lack of statistical significance elsewhere likely reflects inadequate power, smaller sample sizes, or wider CIs rather than a null association. Regional heterogeneity may also be influenced by differences in maternal health service utilisation, socio-economic status and contraceptive coverage. The consistent direction of effect across regions strengthens the robustness and biological plausibility of the findings. Nevertheless, well-designed prospective studies with regionally representative samples and comprehensive adjustment for potential confounders are warranted to elucidate contextual variations and underlying mechanisms.

According to the GRADE assessment, the low certainty of evidence suggests that the true effect is likely close to the estimated effect, although some uncertainty may remain. The relatively low heterogeneity among studies indicates consistent findings across different study settings, which strengthens confidence in the pooled estimate. In addition, the absence of publication bias and the generally low risk of bias among the included studies further support the credibility of the evidence.

However, although a statistically significant association between short interpregnancy interval and PB was noted, the presence of moderate heterogeneity (I²=56.8%) reduces confidence in the pooled estimate. The variability in study designs, study setting and confounding adjustments likely contributed to the observed inconsistency. Therefore, due to the substantial inconsistency and the inherent limitations of observational designs, including residual confounding and potential bias, the overall certainty of evidence was judged to be moderate.

This review employed a standardised methodological approach to examine the association between short interpregnancy intervals and LBW and PB, providing verifiable proofs. However, due to a limited number of primary studies, this meta-analysis did not encompass all regions and administrative cities of Ethiopia, including data from only five of the fourteen regions. Therefore, we recommend further country-wide research to comprehensively assess the effects of short interpregnancy intervals on pregnancy outcomes. Additionally, the definitions employed in this study merit careful consideration. There is no globally applied cut-off for short interpregnancy intervals; while we adopted <24 months in accordance with the WHO’s recommendations, other studies have used <18 months. Variations in these thresholds could influence the comparability of findings across different studies. Furthermore, the classification of interpregnancy intervals, LBW (<2500 g) and PB (<37 completed weeks of gestation) into binary variables, although aligned with international standards, may reduce statistical power and obscure possible dose–response or non-linear relationships. Therefore, the observed relationships should be interpreted with consideration of this methodological limitation.

Conclusion

This meta-analysis presents the association of short interpregnancy interval with adverse neonatal outcomes, specifically LBW and PB. It was concluded that short interpregnancy intervals are significantly associated with PB and LBW. The odds of PB and LBW were significantly higher among women who had short interpregnancy intervals when compared with their counterparts. The findings of this systematic review and meta-analysis provide important evidence that may contribute to achieving the Sustainable Development Goals and improving pregnancy outcomes in Ethiopia. Additionally, healthy policymakers, planners and implementers will use this evidence as a baseline. Therefore, interventions are needed to alleviate such constraint factors. Strategies targeting improving maternal and child health services with community-based and facility-based optimum birth spacing services, including modern family planning services and enhanced breastfeeding (universal access to family planning), are recommended.

Data availability statement

Data are available upon reasonable request.