Mediating role of maternal serum interleukin-1beta and tumor necrosis factor-alpha in the association between environmental tobacco smoke exposure in pregnancy and low birth weight at term

Objectives: To explore the mediation effects of maternal serum interleukin-1 (IL-1) and tumor necrosis factor- (TNF-) on the association between environmental tobacco smoke (ETS) exposure during pregnancy and low birth weight (LBW) at term.Methods: ETS exposure, birth weight, blood sample and covariates were collected from 195 pregnant women delivered term LBW infants and 195 controls delivered normal birth weight infants in two Maternity and Child Hospitals in Guangdong, China. Maternal serum IL-1 and TNF- were measured by flow cytometry. Logistic regression models and path analyses explored the mediation effects of maternal IL-1 and TNF- on the association between ETS exposure and LBW.Results: LBW was significantly associated with maternal ETS exposure (OR=2.14 (95% CI =1.06-4.32)). TNF- and IL-1 were significantly associated with both LBW (OR=1.87 (1.41-2.47) and OR=1.53 (1.14-2.05)) and ETS (=0.32 (0.04-0.60) and =0.27 (0.05-0.49)). Traditional mediation analyses indicated the separate mediation effect of TNF- and IL-1 was 32.2% and 24.6%, respectively. Path analysis revealed the combined mediation effects of TNF- and IL-1 as 29.4% in the pathway from ETS exposure to LBW.Conclusions: Maternal serum IL-1 and TNF- may play a mediating role in the association between maternal ETS exposure during pregnancy and term LBW.