Maternal chronic hepatitis B virus infection and the risk of preterm birth: A retrospective cohort analysis in Chinese women

The association between different clinical states of chronic HBV infection and preterm birth (PTB) is still controversial. A retrospective cohort study among 57,386 pregnant women was conducted to examine the impact of chronic HBsAg positive, both HBsAg and HBeAg positive, and chronic active hepatitis on pregnancy complications related to the overall PTB and its subtypes (spontaneous and iatrogenic). A total of 54,245 pregnancies were included in the final study cohort, among which 2,151(4.0%) pregnant women were HBsAg positive. The PTB rate was 6.0% (129/2151) for HBV-infected women while 4.5% (2319/52094) for those not. Compared with women not infected with HBV, multivariable-adjusted analyses showed HBV-infected women had a 33% higher risk of overall PTB (aRR 1.33 95%CI, 1.11-1.60), a 27% higher risk of spontaneous PTB (aRR 1.27, 95% CI, 1.02-1.57) and a 50% higher risk of iatrogenic PTB (aRR 1.50, 95%CI, 1.07-2.11). The PTB rate was 8.9% (35/395) for both HBsAg and HBeAg-positive women and 16.2% (22/136) for women with active chronic hepatitis. Multivariable-adjusted analyses showed women who were both HBsAg and HBeAg positive had a 47% higher risk of overall PTB (aRR 1.47, 95%CI, 1.04-2.09), a 2.03 times higher risk of spontaneous PTB (aRR 2.03, 95%CI, 1.38-2.99) and a 32% higher risk of iatrogenic PTB (aRR 1.32, 95%CI, 0.62-2.81), while women with chronic active hepatitis had a 3.84 times higher risk of overall PTB (aRR 3.84, 95%CI, 2.42-6.10), a 3.88 times higher risk of spontaneous PTB (aRR 3.88, 95%CI, 2.32-6.45) and a 3.01 times higher risk of iatrogenic PTB (aRR 3.01, 95%CI, 1.22-7.44). Different maternal clinical states of chronic HBV infection are independently associated with an increased risk of overall PTB and its subtypes (spontaneous and iatrogenic).