Oligohydramnios in complicated and uncomplicated pregnancy: a systematic review and meta-analysis

Objective To evaluate adverse pregnancy outcomes in singleton pregnancies diagnosed with oligohydramnios through a systematic review and meta-analysis of controlled trials. Methods We searched electronic databases via OVID, EBSCO, Web of Science, Google Scholar and others from 1980 to 2015. Prospective and retrospective studies with a control group were included. Two authors independently reviewed the abstracts from the literature search. Inclusion criteria were: studies in English, singleton pregnancy, normal fetal anatomy, intact membranes and oligohydramnios determined by the amniotic fluid index (AFI) technique. We stratified the meta-analysis into two groups according to risk: high risk including studies of oligohydramnios with comorbid conditions (e.g. hypertension) and low risk including studies of isolated oligohydramnios. Results Fifteen trials met the inclusion criteria. Nine were high-risk and six were low-risk studies, including 8067 and 27 526 women, respectively. Compared with women with normal AFI, those with isolated oligohydramnios had significantly higher rates of an infant with meconium aspiration syndrome (relative risk (RR), 2.83; 95% CI, 1.38-5.77), Cesarean delivery for fetal distress (RR, 2.16; 95% CI, 1.64-2.85) and admission to the neonatal intensive care unit (NICU) (RR, 1.71; 95% CI, 1.20-2.42). Patients with oligohydramnios and comorbidities were more likely to have an infant with low birth weight (RR, 2.35; 95% CI, 1.27-4.34). However, rates of 5-min Apgar score < 7 (RR, 1.85; 95% CI, 0.69-4.96), NICU admission (RR, 2.09; 95% CI, 0.80-5.45), meconium-stained amniotic fluid (RR, 1.32; 95% CI, 0.62-2.81) and Cesarean delivery for fetal distress (RR, 1.65; 95% CI, 0.81-3.36) were similar to those for women with normal AFI. Stillbirth rates were too low to analyze in the meta-analysis. Conclusions This review helps to delineate which adverse outcomes are increased with oligohydramnios in low-risk pregnancy (NICU admission, Cesarean delivery for fetal distress and meconium aspiration syndrome), but does not provide enough data to determine the optimal timing of delivery in such cases. Oligohydramnios in complicated pregnancy is associated with an increased risk of delivery of an infant with low birth weight, but this may be confounded by the comorbid condition. Therefore, in high-risk pregnancy, management should be dictated by the comorbid condition and not the presence of oligohydramnios. Copyright (C) 2016 ISUOG. Published by John Wiley & Sons Ltd.