目的：探讨孕前体质指数（body mass index, BMI）与早产的关系。方法： 以在北京市海淀区妇幼保健院住院分娩的174例早产儿为病例，382例足月儿为对照，收集孕妇身高、孕前体重、分娩前最后一次体重、孕周、家族史、疾病史以及孕期并发症等信息,运用多因素Logistic回归模型调整混杂因素，分析孕前BMI等因素与早产的关系，并估计调整后的比值比（odds ratio，OR）和95%可信区间（confidence interval，CI）。结果： 通过对早产相关因素的Logistic回归分析，发现孕前肥胖是早产的危险因素，调整后的OR值为2.461（95% CI：1.174~5.159, P=0.017），未发现孕前超重或孕前偏瘦与早产的关联；妊娠期糖尿病、妊娠期高血压和早产儿家族史是早产的危险因素，调整后的OR值分别为1.781（95% CI：1.025~3.095, P=0.040）、3.831（95% CI：2.044~7.180, P<0.001）和3.675（95% CI：1.358~9.942, P=0.010）。结论： 孕前肥胖是早产的危险因素，为了降低早产的发病率，孕妇需要加强孕前保健，在备孕期应控制孕前BMI在正常范围内。

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.