Predictive Value of New Onset Versus Primary Meconium-Stained Amniotic Fluid

Meconium-stained amniotic fluid (MSAF) occurs in up to 52% of postterm pregnancies, 25% of term pregnancies, and 5% of pregnancies <37 weeks of gestation. As a sign of fetal maturity, MFAS may also help signal fetal distress. It is also associated with adverse maternal and neonatal outcomes, including neonatal sepsis, severe fetal acidemia, lower Apgar score, and higher incidence of cesarean delivery (CD). Recent studies have shown that thick meconium increases the risk of adverse outcomes compared with light meconium. Secondary MSAF, or the transition from clear amniotic fluid to meconium, is a common occurrence during labor. However, its clinical importance and prognostic value compared with MSAF at membrane rupture, or primaryMSAF, are unclear. The aim of this study was to examine whether secondary MSAF is a stronger predictor of fetal distress than primary MSAF. This was a cohort study of singleton, term deliveries in a single tertiary medical center in Israel between 2011 and 2018. Data were derived from electronic medical records. Excluded were deliveries involving elective CD, fetus in a breech position, intrauterine fetal death, multiple gestation, and termination of pregnancy. The primary outcome was a composite of adverse neonatal outcome, which included arterial cord blood pH <7.1, 5-minute Apgar score <= 7, or admission to the neonatal intensive care unit, in primary versus secondary MSAF. A total of 56,863 deliveries were included in the analysis: 15.9% had primary MSAF, and 2.6% had secondary MSAF. Secondary MSAF, compared with primaryMSAF, increased the risks of CD (17.8% vs 14%, respectively; P < 0.001) and operative vaginal deliveries (17.6% vs 9.7%; P < 0.001). Secondary MSAF also increased the risks of low 5-minute Apgar score <= 7 (0.8% vs 0.4%; P = 0.015), low arterial cord blood pH (5.8% vs 3.3%; P < 0.001), and duration of hospital stay (4 +/- 1.7 days vs 3.8 +/- 2 days, respectively; P < 0.001). No significant difference was observed in neonatal intensive care unit admission rates, oxygen treatment, hypoglycemia, and meconium aspiration. After controlling for confounders, secondaryMSAFwas independently associated with an increased risk of the composite adverse neonatal outcomes (odds ratio, 1.68; 95% confidence interval, 1.25-2.24; P < 0.001). Parity was associated with a reduced risk of the composite adverse neonatal outcomes (odds ratio, 0.72; 95% confidence interval, 0.63-0.83). In conclusion, secondary MSAF was associated with adverse neonatal outcomes compared with primaryMSAF. This finding suggests a need for greater vigilance for signs of fetal distress in cases of secondary MSAF.