Predictive value of new onset versus primary meconium-stained amniotic fluid

Transition of clear amniotic fluid to meconium-stained fluid is a relatively common occurrence during labor. However, data regarding the clinical significance and the prognostic value of the presence of meconium-stained amnionic fluid (MSAF) are scarce. This study aimed to investigate delivery and neonatal outcomes according to the presence of MSAF and the timing of the meconium passage.

We used an historical cohort study at a single tertiary medical center in Israel between the years 2011 and 2018. Women were divided into two groups according to timing of meconium passage: primary MSAF (MSAF present at membrane rupture) and secondary MSAF (clear amnionic fluid that transitioned to MSAF during labor). Neonatal complication rates were compared between groups. Composite adverse neonatal outcome was defined as arterial cord blood pH <7.1, 5 min Apgar score ≤7, and/or neonatal intensive care unit admission.

The study cohort included 56 863 singleton term births. Of these, 9043 (15.9%) were to women who had primary MSAF, and 1484 (2.6%) to those with secondary MSAF. Secondary MSAF compared with primary MSAF increased the risks of cesarean birth and operative vaginal delivery, increased the risks of low one- and five-minute Apgar scores and low arterial cord blood pH, and increased hospital stay duration. Multivariate analysis revealed that secondary MSAF was independently associated with an increased risk of composite adverse neonatal outcome (OR1.68, 95% CI 1.25-2.24, p < 0.001) compared with primary MSAF.

In this sample, secondary MSAF was associated with more adverse neonatal outcomes than primary MSAF. Closer monitoring of fetal well-being may be prudent in these cases.