Abstract
Background
Amniocentesis is a commonly used invasive diagnostic procedure in prenatal care. Although it has historically been associated with a notable risk of pregnancy loss, advances in ultrasound technology and procedural techniques have significantly improved its safety profile. Understanding current complication rates and related risk factors is essential to support evidence-based patient counseling and informed decision-making.
Methods
We conducted a retrospective cohort study of 1,655 pregnant women who underwent mid-trimester amniocentesis between 2018 and 2023 at a tertiary perinatal referral center. Only singleton pregnancies with normal cytogenetic and anatomical findings were included in the final analysis (n = 917). Data on maternal characteristics, inflammatory markers, and procedural details were collected. Post-procedural complications occurring within 14 days were categorized as mild (e.g., transient abdominal pain, spotting, amniotic fluid leakage) or severe (pregnancy loss). Statistical analysis included descriptive methods and logistic regression to evaluate potential risk factors.
Results
Among the 917 patients included in the analysis, 63 experienced complications, resulting in a total complication rate of 6.87%. The majority of adverse events were classified as mild and self-limiting. Pregnancy loss occurred in four cases (0.43%) within 14 days of the procedure. No statistically significant associations were observed between complications and maternal age, gestational age at the time of the procedure, body mass index, route of amniotic access, inflammatory markers, or the use of prophylactic antibiotics.
Conclusions
Amniocentesis appears to be a safe diagnostic procedure when performed by experienced clinicians in a tertiary care setting. The low rate of severe complications reinforces its role as a dependable tool in prenatal diagnostics. These findings may help reduce patient anxiety and inform risk communication during prenatal counseling.
Keywords: Amniocentesis, Prenatal diagnosis, Pregnancy loss, Complications, Risk factors, Invasive procedure
Background
Amniocentesis is one of the most commonly used invasive procedures in prenatal diagnostics, typically performed during the second trimester of pregnancy [1]. Indications for amniocentesis include genetic abnormalities detected on prenatal ultrasound, a family history of genetic conditions, as well as high-risk results for aneuploidy on first-trimester screening tests. Among non-genetic indications, suspicion of fetal TORCH infection, diagnosis of chorioamnionitis, and assessment of fetal lung maturity account for the majority of cases [2]. Despite the development and increasing availability of non-invasive prenatal testing (NIPT), amniocentesis continues to be the standard invasive method for definitive chromosomal diagnosis [3].
Although considered a relatively safe procedure, amniocentesis is often associated with anxiety and hesitation among patients due to its invasive nature. This may lead to refusal among a substantial number of pregnant women [4]. Historically, the risk of procedure-related pregnancy loss was estimated at approximately 1% [5], which contributed to persistent concerns. However, more recent large-scale studies suggest that the actual risk is significantly lower, with rates of procedure-related miscarriage likely ranging from 0.2% to 0.3% [5–7], particularly when performed by experienced practitioners in high-volume centers. The decrease in overall complication rates is likely related to improvements in ultrasound guidance and evolving procedural techniques. Other procedure-related risks include preterm prelabor rupture of membranes (PPROM) in 1–2%, vaginal bleeding in 2–3%, and, very rarely, chorioamnionitis and needle injury to the fetus (less than 0.1%) [8]. Potential red cell alloimmunization due to the Rhesus factor is now largely prevented by administering Rh immunoglobulin to Rh-negative patients after the procedure [9]. The risk of other mild and self-limiting complications, such as vaginal spotting and abdominal pain, does not exceed a few percent [10].
Understanding the current safety profile of amniocentesis and the influence of various maternal or procedural factors is crucial for improving patient counseling and decision-making during prenatal care. Several factors should be considered when assessing the impact of amniocentesis on the risk of fetal loss, as they may independently increase this risk or be more prevalent among patients referred for invasive testing. According to various authors, these factors include advanced maternal age, smoking, vaginal bleeding during pregnancy, a history of more than three spontaneous miscarriages, prior pregnancy termination, and the presence of uterine fibroids [11–13].
The aim of this study was to evaluate the frequency and severity of post-amniocentesis complications in a tertiary care center, and to identify potential risk factors associated with these adverse outcomes, including maternal characteristics, inflammatory markers, and the route of amniotic access.
Methods
This retrospective cohort study was conducted at a tertiary perinatal referral center and included all pregnant patients (n = 1,655) who underwent mid-trimester amniocentesis between January 2018 and December 2023. Gestational age at the time of the procedure ranged from 15 + 0 to 22 + 6 weeks and was calculated based on the date of the last menstrual period in regularly menstruating women. In cases of date uncertainty or discrepancy, gestational age was determined by crown–rump length (CRL) measured between 11 and 14 weeks of gestation. Multiple pregnancies were excluded from the analysis. The primary objective of the study was to assess the safety profile of the procedure and to identify factors potentially associated with post-amniocentesis complications. All patients received detailed pre-procedural counseling. They were instructed to report to the emergency department in the event of any symptoms suggestive of complications, such as lower abdominal pain, vaginal spotting, or amniotic fluid leakage.
All procedures were performed under ultrasound guidance by experienced perinatologists using 22-gauge spinal needles, which are routinely used in our center. The choice of needle size was based on operator preference and standard practice, aiming to balance sampling efficiency and procedural safety. Each procedure was carried out under sterile conditions in a standardized manner, following internal institutional protocols.
Prophylactic antibiotics were administered to 266 patients. This practice was initially implemented because, during the first two years of the study period, our center routinely administered antibiotic prophylaxis before every amniocentesis, in accordance with the local protocol at that time. In subsequent years, this routine was discontinued. When used, the standard regimen consisted of a single intravenous dose of cefazolin—either 2–3 g, depending on body weight—administered 30 to 60 min before the procedure.
A minority of procedures were presumably performed by obstetricians undergoing maternal–fetal medicine fellowship training under direct supervision. Due to the retrospective nature of data collection, the exact number could not be determined, though it is estimated to be below 10%. This consistently high level of operator expertise contributed to procedural consistency and minimized technique-related variability. Data on the number of needle insertions per procedure were not available due to the retrospective design. However, no procedures were abandoned or failed.
Of the 1,655 patients initially screened, 1,075 delivered at our center and had complete follow-up. Patients who delivered elsewhere or for whom follow-up data were incomplete were excluded. To ensure that observed outcomes were attributable to the procedure itself rather than to underlying fetal conditions, only patients with normal cytogenetic results and no structural anomalies were included in the analysis of post-procedural complications. A total of 158 cases with abnormal karyotypes or fetal malformations were excluded due to their a priori increased risk of pregnancy loss unrelated to amniocentesis (Fig. 1). As a result, 917 patients were included in the final analysis.
Fig. 1.
Patient Flow Chart
Data were retrospectively collected from medical records and included maternal age, gestational age at the time of the procedure, body mass index (BMI), indication for amniocentesis, route of amniotic fluid access, use of prophylactic antibiotic therapy, and inflammatory markers—C-reactive protein (CRP) and leukocyte count (WBC). CRP and WBC were routinely measured within 24 h prior to the procedure. Elevated markers did not preclude amniocentesis unless clinical suspicion of infection was present. The results of genetic testing and fetal anatomical surveys were also documented. Post-procedural complications occurring within 14 days of amniocentesis were recorded. These were classified as mild (including transient lower abdominal pain, vaginal spotting, temporary amniotic fluid leakage, and self-limiting uterine contractions) or severe (pregnancy loss). Only complications reported by patients or documented in hospital records were considered for analysis.
Statistical analysis was performed using PQStat software. Descriptive statistics were used to summarize the data. Associations between selected clinical and procedural variables and the incidence of complications were assessed using the Chi-square test or Fisher’s exact test for categorical variables, and the Student’s t-test or Mann–Whitney U test for continuous variables, based on data distribution. A p-value of < 0.05 was considered statistically significant, and all p-values were rounded to two decimal places. Additionally, logistic regression analysis was performed to calculate odds ratios (ORs) and to evaluate associations between individual factors—including maternal age, gestational age, BMI, route of amniotic fluid access, use of prophylactic antibiotics, CRP levels, and leukocyte count—and the likelihood of post-procedural complications.
In this study, we aggregated all post-procedural complications—both mild and severe—into a single binary outcome variable (“any complication”: yes/no) to allow for consistent examination of potential risk factors. Logistic regression models were applied to explore these associations; however, none of the evaluated variables reached statistical significance.
Since only four patients experienced severe complications, it was not feasible to construct a separate statistical model for this subgroup. Nonetheless, a descriptive review of these cases was performed, and no clear patterns or common characteristics were observed. Given the limited statistical power resulting from the low number of events, these findings should be interpreted with caution. These results highlight the need for larger, multicenter studies to enable more robust analysis of rare but clinically significant outcomes.
Results
Out of the 917 patients included in the final analysis, 63 post-procedural complications were reported, resulting in an overall complication rate of 6.87%. The vast majority were classified as mild, including transient lower abdominal pain, vaginal spotting, and temporary amniotic fluid leakage. The incidence of pregnancy loss within 14 days following the procedure was 0.43% (4 cases), which may be attributable to amniocentesis, although causality cannot be definitively established.
Gestational age
The mean gestational age at the time of amniocentesis was 17.08 weeks (SD = 2.55) in patients without complications and 16.22 weeks (SD = 1.54) in those with complications. No statistically significant difference was found between the two groups (p = 0.10, Student’s t-test), indicating that the timing of the procedure was not associated with the incidence of complications.
Body mass index (BMI)
The mean BMI was 26.18 (SD = 5.0) in the group without complications and 24.18 (SD = 4.9) in the group with complications. Although patients with complications had a modestly lower BMI on average, this difference was not statistically significant (p = 0.14, Student’s t-test).
Maternal age
The mean maternal age in the group without complications was 33.45 years (SD = 5.7), whereas in the group with complications, it was 35.00 years (SD = 5.0). The difference between the groups was not statistically significant (p = 0.88, Student’s t-test), indicating that maternal age was not associated with the risk of post-amniocentesis complications.
Parity
Among patients without complications, 59.62% were multiparous and 40.38% were nulliparous. In contrast, among those with complications, 69.56% were nulliparous and 30.43% were multiparous. Although complications were more frequent in nulliparous women, the difference was not statistically significant (p = 0.17, Chi-square test).
Amniotic access route
Among patients who underwent the transamniotic access route, 4.64% experienced complications, versus 7.94% in the transchorionic group. This difference was not statistically significant (p = 0.18, Chi-square test).
C-reactive protein (CRP)
The mean CRP level in the complications group was 4.49 mg/L (SD = 4.09), compared to 4.25 mg/L (SD = 2.61) in the group without complications. This difference was not statistically significant (p = 0.62, Mann–Whitney U test). Elevated CRP levels (> 5 mg/L) were observed in 14 patients (22.2%) with complications and in 159 patients (18.6%) without complications.
White blood cell count (WBC)
The mean WBC count in the complications group was 9.74 × 10⁹/L (SD = 2.67), versus 9.06 × 10⁹/L (SD = 2.56) in the group without complications. This difference was not statistically significant (p = 0.99, Mann–Whitney U test).
Prophylactic antibiotic therapy
Prophylactic antibiotics were administered to 266 patients (29.0%), among whom 2.63% had complications. In the group without antibiotic prophylaxis (n = 651), the complication rate was 2.46%. This difference was not statistically significant (p = 0.71, Chi-square test).
A multivariate logistic regression model was used to assess the association between selected maternal and clinical variables and the risk of post-amniocentesis complications. No variables were found to be significantly associated with complication risk.
The calculated odds ratios (OR) with 95% confidence intervals (CI) were as follows:
Gestational age: OR = 0.80 (95% CI: 0.61–1.05, p = 0.11)
BMI: OR = 0.93 (95% CI: 0.84–1.02, p = 0.14)
Maternal age: OR = 1.02 (95% CI: 0.95–1.09, p = 0.59)
CRP level: OR = 0.99 (95% CI: 0.88–1.10, p = 0.82)
WBC count: OR = 0.90 (95% CI: 0.76–1.07, p = 0.24)
Transamniotic approach: OR = 0.81 (95% CI: 0.56–1.17, p = 0.26)
Transchorionic approach: OR = 1.77 (95% CI: 0.75–4.15, p = 0.19)
Antibiotic prophylaxis: OR = 1.07 (95% CI: 0.44–2.57, p = 0.87)
The results are also presented graphically in a forest plot (Fig. 2), showing that all confidence intervals crossed the null value (OR = 1), further supporting the lack of significant associations.
Fig. 2.
Logistic Regression Plot
Among the four patients who experienced severe complications—defined as pregnancy loss following amniocentesis despite normal cytogenetic results and absence of structural anomalies—the mean maternal age was 37.25 years (SD = 2.22), compared to 33.45 years (SD = 5.7) in those without complications. The mean gestational age at the time of the procedure was 15.5 weeks (SD = 0.58) in patients with severe complications and 17.08 weeks (SD = 2.55) in those without complications. The mean BMI was 23.27 (SD = 3.23) in the severe complication group, versus 26.18 (SD = 5.0) in the non-complication group. The mean CRP level was modestly elevated in patients with severe complications (4.73 mg/L, SD = 2.98) compared to those without complications (4.25 mg/L, SD = 2.61). The mean WBC count was 9.45 × 10⁹/L (SD = 2.53) in the severe group versus 9.06 × 10⁹/L (SD = 2.56) in the non-complication group. Among the four patients with severe complications, one had elevated CRP, one had elevated WBC count, and two had normal inflammatory markers. Due to the small number of events, no meaningful statistical comparisons could be made, and these findings should be interpreted with caution.
Due to the limited number of cases, no formal statistical testing was performed in this subgroup, as there was a high risk of bias and spurious associations. Instead, findings are presented descriptively. A trend was observed suggesting that pregnancy loss tended to occur at slightly earlier gestational ages. While this observation should be interpreted with caution, it may indicate a potential association worth further investigation in larger, adequately powered studies.
Discussion
This retrospective analysis reinforces the evidence that amniocentesis demonstrates a favorable safety profile when performed by experienced clinicians in a tertiary care setting. In our cohort, the overall complication rate was 6.87%, and the majority of complications were mild and self-limiting, including lower abdominal pain, transient vaginal spotting, and temporary leakage of amniotic fluid. Severe complications were rare: only 0.43% of patients with normal karyotypes and no structural anomalies experienced pregnancy loss within 14 days following the procedure.
Historically, the risk of procedure-related pregnancy loss was estimated at approximately 1%, based on studies conducted in the 1980s and 1990s [5–7]. These early estimates likely reflected greater procedural variability, limited use of ultrasound guidance, and differences in operator experience and technique. More recent studies, including those by Akolekar et al. [14] and Wulff et al. [15], report considerably lower complication rates, typically ranging from 0.1% to 0.3%, which aligns closely with our findings.
Several factors have been identified as potentially contributing to the risk of complications following amniocentesis, including gestational age at the time of the procedure, multiple needle insertions, posterior placentation, maternal BMI, and elevated inflammatory markers [16]. Operator expertise and procedural standardisation have been shown to reduce complication rates significantly [17]. The low rate of pregnancy loss observed in our study may help explain the impact of consistent technique, real-time ultrasound guidance, and exclusive performance of procedures by experienced specialists.
In our analysis, no evaluated clinical or maternal variables—including maternal age, gestational age, BMI, CRP levels, white blood cell count, or route of amniotic access—were found to be significantly associated with the occurrence of complications. Prophylactic antibiotic use was not associated with complication rates, indicating that routine administration may not be warranted in low-risk cases.
A key strength of this study is the large, well-documented cohort from a single high-volume center, which ensured uniform procedural conditions and consistent follow-up. However, several limitations must be acknowledged. The retrospective design relies on the accuracy and completeness of medical records, which may introduce information bias. Additionally, 580 patients were excluded due to incomplete follow-up, potentially introducing selection bias related to loss to follow-up. This may have led to underestimation of complication rates in patients who delivered elsewhere or were lost to observation.
Despite these limitations, our findings provide meaningful reassurance regarding the safety profile of amniocentesis and may contribute to reducing patient anxiety through informed, evidence-based counselling. Future prospective studies are warranted to identify subtle or context-specific risk factors not captured in this dataset and to further refine clinical recommendations for distinct patient subgroups. The predominance of mild complications in our cohort may have limited the ability to detect significant associations between patient characteristics and adverse outcomes. Future research should consider stratified analyses focusing specifically on severe complications.
Conclusions
Amniocentesis continues to be a safe and reliable diagnostic procedure in prenatal care. In this retrospective analysis of 917 patients with complete follow-up and pregnancies without structural or genetic abnormalities, the overall complication rate was low (6.87%), with most adverse events being mild and self-limiting. The incidence of pregnancy loss was very low (0.43%), supporting the favorable safety profile of the procedure.
We found no statistically significant associations between post-procedural complications and maternal age, gestational age, BMI, inflammatory markers, route of amniotic access, or the use of prophylactic antibiotics. Our findings support the safety of amniocentesis when clinically indicated and provide valuable evidence to inform counselling of patients who may experience anxiety about the procedure.
Acknowledgements
The authors thank the staff of the Department of Reproduction and Perinatal Medicine for their assistance in patient care and data retrieval.
Authors’ contributions
All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Świetlicki and Paluszkiewicz-Kwarcińska. The first draft of the manuscript was written by Świetlicki and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Data availability
The datasets generated and analysed during the current study are available from the corresponding author on reasonable request.
Declarations
Ethics approval and consent to participate
This study was a retrospective analysis of routinely collected clinical data. The study protocol was reviewed and approved by the Bioethics Committee of Poznan University of Medical Sciences, Poznań, Poland.
The study was conducted in accordance with the principles of the Declaration of Helsinki.
Due to the retrospective nature of the study and the use of anonymized data, the requirement for informed consent to participate was waived by the Bioethics Committee of Poznan University of Medical Sciences, in accordance with applicable national regulations.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets generated and analysed during the current study are available from the corresponding author on reasonable request.