Association between borderline amniotic fluid levels and adverse perinatal outcome: systematic review and meta‐analysis
Bibliographic record
Abstract
OBJECTIVES: The aim of the present study was to evaluate adverse perinatal outcomes in low-risk singleton pregnancies with borderline oligohydramnios. METHODS: A comprehensive literature search was conducted for observational cohort studies that compared perinatal outcomes in low-risk singleton pregnancies between those with borderline oligohydramnios, defined as an amniotic fluid index (AFI) of 5.1-8.0 cm, and those with a normal AFI. EMBASE, MEDLINE and Web of Science databases were searched for studies published from inception to July 2024. The quality of the studies was assessed using the Newcastle-Ottawa Scale. Meta-analyses were performed using a random-effects model to calculate pooled proportions and 95% CIs for each outcome in both groups. The outcomes assessed included overall Cesarean delivery (CD), CD owing to fetal distress, 5-min Apgar score < 7, low birth weight (LBW), admission to the neonatal intensive care unit (NICU), meconium-stained amniotic fluid, meconium aspiration syndrome, non-reassuring fetal heart rate during labor, operative vaginal delivery and neonatal death. RESULTS: The search yielded 6902 results, of which eight met the inclusion criteria for the meta-analysis. From these eight studies, 799 singleton pregnancies with borderline oligohydramnios and 1512 singleton pregnancies with normal AFI were analyzed. Analysis revealed an association of borderline oligohydramnios with increased risks of overall CD (odds ratio (OR), 2.20 (95% CI, 1.70-2.84); P < 0.01), CD owing to fetal distress (OR, 2.70 (95% CI, 1.70-4.30); P < 0.01), 5-min Apgar score < 7 (OR, 2.18 (95% CI, 1.38-3.44); P < 0.01), LBW (OR, 2.32 (95% CI, 1.27-4.25); P < 0.01) and NICU admission (OR, 2.63 (95% CI, 1.63-4.24); P < 0.01), compared with normal AFI. A sensitivity analysis that included only term pregnancies revealed significantly higher risks of overall CD, CD owing to fetal distress, LBW and NICU admission in those with borderline oligohydramnios compared to those with normal AFI. Among the pregnancies in which AFI was measured within 1 week before delivery, the risks of overall CD and CD owing to fetal distress were significantly higher. CONCLUSIONS: We report an association of borderline oligohydramnios with adverse perinatal outcomes among low-risk singleton pregnancies. The increased risks of these perinatal outcomes highlight the need for more frequent monitoring in pregnancies with borderline oligohydramnios. Further research is required to understand the potential benefits and risks of early labor induction and to develop specific guidelines for managing borderline oligohydramnios. © 2025 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.009 | 0.026 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.016 | 0.027 |
| Bibliometrics | 0.005 | 0.007 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".