Meconium stained amniotic fluid exposure is associated with lower rates of respiratory morbidity in offspring

Objective
Meconium stained amniotic fluid (MSAF) effects approximately 1 in every 7 pregnancies, and is a well- established risk factor for short-term respiratory complications in neonates. Little is known regarding long-term respiratory morbidity among these children, as lung growth continues throughout the first decade of life. We investigated the possible impact of MSAF presence during labor and delivery on long-term respiratory morbidity of the offspring, during childhood and adolescence

Study Design
A population-based prospectively analyzed cohort study was performed, including all singleton deliveries occurring between 1991-2014 at a single tertiary medical center. Fetuses with congenital malformations were excluded. Exposure was defined as presence of MSAF during labor and delivery. Hospitalizations of the offspring up to the age of 18 years involving respiratory morbidities were evaluated. A Kaplan Meier survival curve was used to compare cumulative morbidity incidence. A Cox hazards regression model was used to control for confounders.

Results
During the study period 242,342 deliveries met the inclusion criteria. Of them, 14.7% (n=35,609) deliveries involving MSAF were documented. Rate of respiratory related hospitalizations, up to the age of 18 years, was significantly lower in children exposed to MSAF as compared with the unexposed group (4.5% vs. 4.9%, respectively, p=0.001, Table). Specifically, hospitalizations involving pneumonitis were significantly less common among the MSAF group (OR 0.5, 95%CI 0.13-0.96, p=0.034). The Kaplan Meier survival curve demonstrated significantly lower total cumulative respiratory morbidity rates in the MSAF exposed group (Figure, log rank p<0.001). In the Cox regression model, controlled for maternal age, diabetes, hypertension, gestational age at birth and delivery mode, MSAF exhibited an independent and significant protective effect on long-term childhood respiratory morbidity (adjusted HR 0.91, 95%CI 0.86-0.96, p<0.001).

Conclusion
Fetal exposure to MSAF during labor and delivery appears to be associated with lower rates of long- term respiratory related hospitalizations in the offspring. Changes in offspring microbiome possibly resulting from exposure to MSAF during labor and delivery, may offer an explanation for these findings.