Maternal age and educational level modify the association between chronic hepatitis B infection and preterm labor

BACKGROUND: Few studies have investigated whether maternal age and education level modify the association of chronic hepatitis B virus (HBV) infection with preterm labor. We hypothesized that the association of HBV infection with preterm labor is modified by maternal age and education level. METHODS: A retrospective cohort study was conducted on the HBsAg-positive and HBsAg-negative pregnant women delivered from June 2012 to August 2017 at Wuhan Medical Care Center for Women and Children, Wuhan, China. A multivariate regression model was used in this study. RESULTS: This study included 2050 HBsAg-positive pregnant women and 2050 HBsAg negative women. In the stratified analyses, positive HBsAg status was associated with the increased risk of preterm labor in women aged < 30 years, having low educational level, with an odds ratio of 1.65(95% CI 1.07–2.54) and 2.59(95% CI 1.41–4.76), respectively. Breslow-Day test showed that there existed significant differences in the ORs for HBsAg carriage across each stratum of maternal age (p = 0.023), educational level (p = 0.002). After adjusting other co-variables, we observed maternal HBV infection (OR 1.60, 95% CI 1.03–2.49) was still associated with risk of preterm labor in pregnancy women with age < 30. Similarly, the significant association of HBV infection (OR 2.49, 95% CI 1.34–4.63) with preterm labor remained in low educated women. CONCLUSIONS: Our results indicated that HBV infection was associated with high risk of preterm labor, but maternal age and educational level could modify the association between HBV infection and preterm labor.