Meconium-stained amniotic fluid during labor may be a protective factor for the offspring's childhood wheezing up to 3 years of age: the Japan Environment and Children's Study.

UNLABELLED: We aimed to evaluate the association between meconium-stained amniotic fluid during labor and offspring's childhood wheezing. This study analyzed the data of participants enrolled in the Japan Environment and Children's Study, a nationwide prospective birth cohort study, between 2011 and 2014. Data of women with singleton live births between 22 and 40 weeks' gestation were analyzed. Participants were categorized into two groups according to the presence or absence of meconium-stained amniotic fluid. The primary outcome measure was the offspring's childhood wheezing up to 3 years of age. A logistic regression model was used to calculate the adjusted odds ratio for childhood wheezing in children of women with meconium-stained amniotic fluid, considering those without meconium-stained amniotic fluid as a reference, taking into account the potential confounding factors affecting the incidence of wheezing. We analyzed data from 61,991 participants: 1796 (2.9%) participants had meconium-stained amniotic fluid during labor and 18,919 (30.5%) of the offspring had childhood wheezing. The adjusted odds ratios for the offspring's childhood wheezing were 0.89 (95% confidence interval, 0.79-0.99) in total participants, 0.87 (95% confidence interval, 0.78-0.97) in term births, and 2.00 (95% confidence interval, 0.98-4.09) in preterm births.

CONCLUSIONS: This study revealed a decreased incidence of childhood wheezing among the children of women with meconium-stained amniotic fluid in term births. By yet unknown mechanisms, meconium-stained amniotic fluid was associated with a decreased incidence of childhood wheezing in the offspring. Further studies are required to clarify the mechanism of one's own meconium in affecting their health condition.

WHAT IS KNOWN: • Meconium-stained amniotic fluid during labor is associated with several adverse perinatal outcomes, and meconium aspiration syndrome is associated with offspring's childhood asthma and wheezing. • Meconium-stained amniotic fluid during labor could be an independent protective factor for the offspring's dermatitis and skin rash.

WHAT IS NEW: • Whole cases with meconium-stained amniotic fluid during labor were associated with a decreased incidence of offspring's childhood wheezing up to 3 years of age. • This study may shed light on the effects of simple meconium-stained amniotic fluid on offspring's childhood health.