Prevalence of preterm birth and risk factors associated with it at different gestational ages: A multicenter retrospective survey in China

OBJECTIVES: To investigate the prevalence of preterm birth (PTB) and the risk factors for different gestational age subgroups of preterm birth in China. METHODS: We carried out a descriptive cross-sectional study encompassing all singleton live births (24(+0) to 41(+6) weeks) with completed data in 23 provinces in China from 2010 to 2017 during investigation period. We compared both the preterm group (24(+0) to 36(+6) weeks) and preterm subgroups (<32 weeks, 32(+0) to 33(+6) weeks, and 34(+0) t0 36(+6) weeks) with the term group (37(+0) to 41(+6) weeks). We collected information on maternal and fetal characteristics from medical records. Logistic regression was use. RESULTS: The prevalence of PTB was 7.4% (15,833/215,254) in singleton births. After adjusting for maternal age, parity, and potential risk factors in univariate analysis, the high-risk factors for PTB at <32 weeks were placental abruption (aOR=41.52; 95% CI, 25.89–66.58), placenta previa (aOR=40.04; 95% CI, 32.00–50.09), chorioamnionitis (aOR=11.06; 95% CI, 8.738–14.02), and hypertension disorders in pregnancy (HDP) (aOR=3.564; 95% CI, 2.930–4.335). Intrahepatic cholestasis of pregnancy (ICP) was significantly associated with PTB at 34–36 weeks (aOR=5.763; 95% CI, 5.049–6.577), particularly with spontaneous PTB (aOR=10.04; 95% CI, 8.79–11.47). Gestational diabetes mellitus (GDM) was significantly associated with PTB at 34–36 weeks only (aOR=1.156; 95% CI, 1.054–1.267). CONCLUSION: Placental abruption, placenta previa, chorioamnionitis, and HDP were more predictive of early PTB; GDM and ICP were more predictive of late PTB.