Amniotic fluid transitioning from clear to meconium stained during labor—prevalence and association with adverse maternal and neonatal outcomes

Objective: The objective of this study is to compare pregnancy outcomes in deliveries complicated by primary meconium-stained amniotic fluid (MSAF, present at membrane rupture) and secondary MSAF (transitioned from clear to MSAF during labor). Methods: The medical records and neonatal charts of all deliveries ≥ 37^0/7 weeks between October 2008 and July 2018 were reviewed. The primary outcome was composite adverse neonatal outcome that included early neonatal complications. Results: Of 30,215 deliveries during the study period, 4302 (14.2 %) were included: 3845 (89.4%) in the primary MSAF group and 457 (10.6%) in the secondary MSAF group. The rate of the primary outcome was higher in the secondary MSAF group (p = 0.006). This association remained significant after controlling for background confounders. The secondary MSAF group had higher rate of cesarean deliveries (CDs) and assisted vaginal deliveries. There was a higher rate of composite adverse neonatal outcome when secondary MSAF was diagnosed < 3 vs. >3 h before delivery (p = 0.004). Conclusion: Secondary MSAF was associated with higher rates of adverse neonatal outcome, CDs, and assisted vaginal deliveries, compared with primary MSAF.