The risk factors of preterm birth: A multicentre case-control survey in China in 2018

Objectives: To investigate the risk profile of preterm birth (PTB) in 2018 in China.

Method: A prospective multicentre case-control study was conducted in 15 hospitals located in seven provinces throughout three geographical areas (the Eastern, South-Central and North-Western regions) in China. A total of 3147 preterm (<37⁺⁰ weeks) and 3147 term (37⁺⁰ to 41⁺⁶ weeks) live-birth mothers were included. Designed questionnaires were used to investigate maternal and fetal information. We calculated multivariable logistic regression and population attributable risk (PAR).

Results: Iatrogenic PTB accounted for 48.1% of preterm mothers. Multivariable analysis showed PTB was significantly associated with six categories of maternal and fetal factors, adverse life-style and psychological conditions (adjusted odds ratio (aOR) 2.063, 95% confidence interval (CI) 1.601-2.657) had the highest PAR% (60.1%). High school and below education level (PAR% = 25.8%), living in town or village (PAR% = 24.4%), low pregnant weight gain (PAR% = 16.8%), hypertensive disorders in pregnancy (aOR: 5.010, 95% CI: 4.039-6.216, PAR% = 15.3%), placental abnormality (aOR: 4.242, 95% CI: 3.454-5.211, PAR% = 14.1%) and multiple pregnancy (aOR: 10.990, 95% CI: 7.743-15.599, PAR% = 11.8%) were significantly associated with PTB with high PAR% value.

Conclusion: The main risk factors for PTB in China were placental abnormality, hypertensive disorders in pregnancy and multiple pregnancy. Adverse life-style and psychological conditions and socio-economic disadvantage had high public health significance.