Objective: To study the relationship between pre-pregnancy body mass index (BMI) and preterm birth.
Methods: A case-control study was conducted in Haidian Maternal and Child Health Hospital in Beijing from January to April in 2013. This study contained 174 preterm births in the case group and 382 term deliveries in the control group. The height, pre-pregnancy body weight, body weight before delivery, gestational weeks, history of diseases, family history of diseases, and complications during pregnancy of the subjects were collected. Multivariate Logistic regression was used to estimate the odds ratio and 95% confidence intervals (CI) after adjustment by maternal age, education, smoke during pregnancy, primiparous, mean income, and mean family living space.
Results: After analyzing the relevant risk factors of preterm birth, the multivariate Logistic regression showed that pre-pregnancy obesity was a risk factor for preterm birth, the adjusted odds ratio was 2.461 (95% CI: 1.174-5.159, P=0.017). The associations between pre-pregnancy overweight and preterm birth or pre-pregnancy underweight and preterm birth were not found. The gestational diabetes mellitus, pregnancy-induced hypertension, and family history of preterm birth were risk factors for preterm birth, the adjusted odds ratios were 1.781 (95% CI: 1.025-3.095, P=0.040), 3.831 (95% CI: 2.044-7.180, P<0.001), and 3.675 (95% CI: 1.358-9.942, P=0.010), respectively.
Conclusion: Pre-pregnancy obesity appeared to be a risk factor for preterm birth. To decrease the incidence of preterm birth, women should improve preconception care and keep their BMI in a normal range before pregnancy.