Maternal and neonatal outcomes in primary vs. secondary meconium-stained amniotic fluid

We aimed to compare obstetrical and neonatal outcomes between women with primary meconium-stained amniotic fluid (MSAF), which presents at membrane rupture, and women with secondary MSAF, which appears after rupture of initially clear fluid.

This retrospective cohort study included all singleton deliveries at ≥37 weeks gestation with MSAF, at a tertiary university-affiliated hospital between March 2020 and July 2024. Multiple pregnancies, preterm deliveries and elective cesarean deliveries (CD) were excluded. The primary outcome was a composite of adverse neonatal events, including low Apgar scores, umbilical artery pH < 7.15, admission to the neonatal intensive care unit, meconium aspiration syndrome, and neonatal death.

Of 2142 women with MSAF, 128 (6 %) had secondary MSAF. Secondary compared to primary MSAF was associated with higher rates of CD (26.6 % vs 14.9 %, p < 0.001), CD due to fetal distress (24.2 % vs. 12.9 %, p = 0.001), operative deliveries (7.8 % vs. 3.8 %, p < 0.001), admission to the neonatal intensive care unit (8.6 % vs. 3.4 %, p = 0.007), and respiratory support (7.0 % vs. 3.0 %, p = 0.034). The composite adverse neonatal outcome was more frequent following secondary MSAF (30.5 % vs 15.7 %, p < 0.001), particularly in deliveries beyond 40 weeks (40.0 % vs. 22.1 %, p = 0.035). In multivariate analysis, secondary MSAF was an independent risk factor for the composite adverse neonatal outcome (odds ratio 1.73, 95 % CI = 1.13-2.67, p = 0.012) after adjustment for potential confounders.

Compared to primary MSAF, secondary MSAF, especially after 40 weeks of gestation was associated with worse neonatal outcomes. This supports the role of secondary MSAF as a potential marker of adverse neonatal outcomes.