Perinatal outcomes of isolated oligohydramnios at term and post-term pregnancy: a systematic review of literature with meta-analysis.

OBJECTIVE: The management of isolated oligohydramnios (IO) in post/term pregnancies is controversial. The aim of this paper was to review outcomes of term and post-term pregnancies with IO versus normal amniotic fluid (AF) at labor assessment.

STUDY DESIGN: A search in PubMed, Medline, EMBASE, and reference lists was performed. Inclusion criteria for articles selection: singleton pregnancy, definition of olgohydramnios as AFI <5cm, AF assessment at 37-42 gestational weeks.

EXCLUSION CRITERIA: fetal malformations, preterm delivery, premature rupture of membranes, intrauterine growth restriction. Perinatal outcomes were: obstetric intervention for non-reassuring fetal heart rate (cesarean section, operative delivery), meconium-stained AF, Apgar score <7 at 5min, umbilical artery pH <7.0, small for gestational age infants (SGA), admission to neonatal intensive care unit (NICU) and perinatal death. Meta-analysis compared outcomes of pregnancies with IO vs normal AF. Inter-studies heterogeneity was tested. Pooled odds ratio (OR) and 95% confidence interval (95% CI) were calculated. Differences between the two groups were considered significant if 95% CI did not encompass 1. MOOSE guidelines were followed.

RESULTS: Four articles provided 679 (17.2%) cases with IO and 3264 (82.8%) with normal AF. Obstetric interventions occurred more frequently in the IO than normal AF group (IO: 89/679, 13% vs normal; AF: 166/3354, 5%; OR: 2.30; 95% CI: 1.00-5.29). Meta-analysis did not show differences with regard to meconium, Apgar, pH, SGA, NICU and perinatal death.

CONCLUSION: In term or post-term pregnancies, IO is associated with increased risk of obstetric interventions but outcomes are similar to those of pregnancies with normal AF.