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.