Associations between maternal complications during pregnancy and childhood asthma: a retrospective cohort study in southern China

Background The associations between maternal complications during pregnancy and childhood asthma have rarely been investigated in low and middle-income countries. We aimed to investigate the associations among the southern Chinese population, and to determine whether the associations were mediated through preterm birth, cesarean delivery, low birth weight and non-breasting feeding in the first 6 months or modified by childs lifestyles (smoking, body mass index(BMI), and sleep duration). Methods We conducted a retrospective cohort study of 208,190 children in Guangzhou, China. Information on maternal gestational hypertension, gestational diabetes, gestational anemia, and hepatitis B during pregnancy was extracted from medical records. Ever diagnosis of asthma of the children was obtained by questionnaire. We used binomial logistic regression models to estimate the adjusted odds ratios (aORs) and 95% confidential interval (CI) for childhood asthma. We conducted mediation analyses to estimate the indirect effects of gestational complications on childhood asthma mediated through preterm birth, cesarean delivery, low birth weight, and non-breastfeeding in the first 6 months. Findings The overall prevalence of ever diagnosed asthma was 1.3%. Gestational hypertension, gestational diabetes, gestational anemia, or hepatitis B during pregnancy was positively associated with ever diagnosed childhood asthma, with the aOR of 1.66(95%CI 1.31-2.10), 1.68(95%CI 1.40-2.02), 1.69(95%CI 1.49-1.91) and 1.54(95%CI 1.13-2.08), respectively. A stronger association was observed for 2 or more gestational complications (aOR= 2.34, 95%CI 1.71-3.23) than 1 gestational complication (aOR=1.80, 95%CI 1.62-1.99). The associations between maternal complications and childhood asthma did not differ by childs smoking, BMI, or sleep duration, except that the aOR for maternal gestational hypertension was significantly higher in children who were active smoker (aOR=5.68, 95%CI 2.09-15.42) than those who were non-smoker (aOR=1.56, 95%CI 1.21-2.00). A small proportion of the associations were mediated through preterm birth, cesarean delivery, low birth weight, and non-breastfeeding in the first 6 months. Interpretation Gestational hypertension, diabetes, anemia, or hepatitis B during pregnancy was significantly associated with childhood asthma in the southern Chinese population, and the associations were partially explained by the mediation effects of cesarean delivery, preterm birth, low birthweight and non-breastfeeding in the first 6 months.