Meconium stained amniotic fluid exposure is associated with a lower rate of offspring's infectious morbidity

Objective
Meconium stained amniotic fluid (MSAF) is a well-established risk factor for immediate adverse neonatal outcomes, and was recently found to be associated with an increased incidence of microbial invasion to the amniotic cavity. We aimed to determine whether MSAF exposure during labor and delivery with its potential effect on offspring microbiome, carries a longer lasting impact on pediatric infectious morbidity.

Study Design
A population-based prospective cohort analysis 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 infectious diseases 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 249,840 deliveries met the inclusion criteria. Of them, 36,914 (14.8%) involved MSAF. Rate of infectious related hospitalizations of the offspring up to the age of 18 years, was significantly lower in children exposed to MSAF as compared with the unexposed group (10.6% vs. 11.1%, respectively, p<0.05). Specifically, hospitalizations involving respiratory infections were significantly less common among the MSAF group (OR 0.88, 95% CI 0.84-0.93, p<0.001, Table). The survival curve demonstrated significantly lower cumulative infectious morbidity rates in the MSAF exposed group (Figure, log rank p<0.001). In the Cox regression model, controlled for maternal age, diabetes, hypertension, mode of delivery and gestational age at birth, MSAF exposed children exhibited an independent association with long-term childhood infectious morbidity (adjusted HR 0.94, 95%CI 0.91-0.97, p<0.001).

Conclusion
Fetal exposure to MSAF during labor and delivery appears to be associated with lower rates of long term infectious related hospitalizations in the offspring. Different microbial interactions with the host immune system, resulting from MSAF exposure, may explain the observed long term protective effect.