Chronic hepatitis B virus infection and preterm labor(birth) in pregnant women-an updated systematic review and meta-analysis.

We aimed to explore whether maternal chronic hepatitis B virus (HBV) infection certainly affects preterm labor (birth) in pregnant women. Four databases were systematically searched up to May 31, 2017, without language restriction. Any study was included if it clearly defined exposure to chronic HBV infection, reported risk of preterm labor or birth in pregnant women, and reported relative risks (RRs) or odds ratios (ORs) or provided data for estimation. RRs (or ORs) with 95% confidence intervals were pooled using random-effects models. Statistical heterogeneity was assessed with Cochran's Q statistic and I2 statistic. Twenty-two observational studies involving 6 141 146 pregnant women (three prospective cohort studies, n = 1 116 799; 15 retrospective cohort studies, n = 5 022 513 and four case-control studies, n = 1834) were included. The risk of preterm labor was significantly intensified with chronic HBV infection compared with uninfected women, with substantial heterogeneity. Chronic HBV infection was also significantly associated with a 16% increase in the risk of preterm birth, with substantial heterogeneity. The risk of preterm birth significantly increased by 21% in HBsAg+/HBeAg+ pregnant women compared with uninfected pregnant women. Chronic HBV infection intensifies the risk of preterm labor and birth in pregnant women, but this conclusion should be interpreted with caution given the possibility of residual confounding and be confirmed by well-designed studies in the future.