目的 探讨双胎妊娠母亲孕前体重指数（body mass index, BMI）水平对母婴结局的影响。 方法 回顾性纳入2018年1月—2020年12月全国21家三级甲等医院出生且有完整记录资料的4 824对双胎新生儿及其孕母为研究对象，按孕母孕前BMI不同分为消瘦组（<18.5 kg/m²，566对）、正常组（18.5~<24 kg/m²，3 120对）、超重组（24~<28 kg/m²，892对）、肥胖组（≥28 kg/m²，246对），比较各组出现不良母婴结局的差异及其关系。 结果 超重组的胎龄低于正常组和消瘦组，但极早产率较高（P<0.008）。相较于正常组和超重组，消瘦组新生儿出现小于胎龄儿比例较高（P<0.008）。校正混杂因素后，与正常组和消瘦组相比，肥胖组妊娠糖尿病及妊娠期高血压疾病的发生风险均较高（P<0.001）。与正常组相比，消瘦组双胎小于胎龄儿的发生风险较高（P<0.05）。 结论 双胎妊娠孕母孕前BMI水平对母婴结局有着密切的影响，该研究为双胎妊娠的个体化体重管理提供了循证依据。

Objective To investigate the impact of maternal prepregnancy body mass index (BMI) on maternal and infant outcomes in twin pregnancies. Methods A retrospective analysis included 4 824 twin pairs and their mothers with complete records, delivered at 21 tertiary grade-A hospitals nationwide from January 2018 to December 2020. Participants were grouped by prepregnancy BMI: underweight (<18.5 kg/m²; n=566), normal weight (18.5 to <24.0 kg/m²; n=3 120), overweight (24.0 to <28.0 kg/m²; n=892), and obese (≥28.0 kg/m²; n=246). Differences and associations in adverse maternal and infant outcomes were compared among groups. Results The gestational age in the overweight group was lower than in the normal and underweight groups, with a higher rate of very preterm birth (P<0.008). Compared with the normal and overweight groups, the proportion of small-for-gestational-age (SGA) neonates was higher in the underweight group (P<0.008). After adjustment for confounders, the obese group had higher risks of gestational diabetes mellitus and hypertensive disorders of pregnancy than the normal and underweight groups (all P<0.001). Compared with the normal group, the underweight group had a higher risk of SGA among twins (P<0.05). Conclusions Maternal prepregnancy BMI is closely associated with maternal and infant outcomes in twin pregnancies, providing evidence-based support for individualized weight management.