Analysis of factors related to preterm birth: a retrospective study at Nanjing Maternity and Child Health Care Hospital in China

Preterm birth is the most important cause of neonatal mortality and morbidity worldwide. The aim of this study was to identify factors associated with preterm birth and examine the heterogeneity and interactions between these factors. We collected data from 1607 pregnant women treated at Nanjing Maternity and Child Health Care Hospital in China. The women included in the study were divided into the full-term group and the preterm-birth group. We used t-tests to compare the characteristics of age and body mass index, Chi-square tests for the other variables, and we used the Wald test to calculate the interaction between factors that may affect preterm birth. The heterogeneity test was used to study the relationship between subgroups. Multivariable logistic regression analysis was used to explore the associations between risk factors and preterm birth, which included all risk factors. All tests were 2-tailed, P < 0.05 was considered significant, and 95% confidence intervals were estimated for percentages. There was no statistical difference in basic characteristics such as age between the full-term and preterm groups. We found 6 independent risk factors that were associated with preterm birth (P < .05): preeclampsia (PE), intrahepatic cholestasis, premature rupture of the membranes (PROM), placenta previa, chorioamnionitis, and scarred uterus. Five combinations of these factors were statistically significant (P < .05) in terms of heterogeneity: PE and PROM; placenta previa and polyhydramnios; chorioamnionitis and PE; PROM and maternal body mass index; and PROM and gestational diabetes mellitus. Ultimately, the 2 subgroups that showed interactions were PE and PROM and chorioamnionitis and PE. The interaction between different factors over the course of preterm birth cannot be ignored. When independent risk factors are combined with other diseases, such as PE combined with PROM or chorioamnionitis in this study, it may more likely result in preterm birth. Thus, this situation deserves particular clinical attention.