Risk factors and birth outcomes of preterm birth subtypes: a case-control study of singleton natural pregnancy

Objective The objective of the study was to identify the risk factors correlated with spontaneous preterm birth (SPTB) and iatrogenic preterm birth (IPTB), as well as to compare the pregnancy outcomes between SPTB and IPTB. Materials and methods A total of 1676 (343 SPTB, 144 IPTB and 1189 full-term control group) cases were collected from the International Peace Maternity & Child Health Hospital of Shanghai between August 2018 and October 2020. A case-control study was conducted to explore the risk factors and pregnancy outcomes of SPTB and IPTB. Results The study identified a set of risk factors for SPTB and IPTB, as well as differences in pregnancy outcomes. Reproductive tract infections and myoma of the uterus were the risk factors for SPTB (p<0.05). Fetal growth restriction, pre-eclampsia, intrahepatic cholestasis of pregnancy, fetal distress, placenta abnormality, oligohydramnios and scarred uterus were the risk factors for IPTB (p<0.05). Antenatal haemorrhage and placental abruption were the risk factors both for SPTB and IPTB (p<0.05). The pregnancy outcomes of the two PTB subtypes differed, and birth weight, length and 1-minute Apgar score of newborns were significantly lower in IPTB than in SPTB (p<0.05). Conclusion The risk factors of SPTB and IPTB are different, and IPTB is associated with a higher incidence of worse pregnancy outcomes than SPTB.