LAUSR

Abstract Objective  The purpose of our study was to evaluate the body mass index (BMI)-specific association between early gestational weight gain (GWG) in dichorionic twin pregnancies and the risk of preeclampsia. Study Design  We conducted a retrospective cohort study of all dichorionic twin pregnancies from 1998 to 2013. Data were obtained from a perinatal database and chart abstraction. Prepregnancy BMI was categorized as normal (18.5–24.9 kg/m 2 ), overweight (25–29.9 kg/m 2 ), and obese (≥30 kg/m 2 ). Early GWG was defined as the last measured weight from 16 0/7 to 19 6/7 weeks' gestation minus prepregnancy weight. GWG was standardized for gestational duration using BMI-specific z -score charts for dichorionic pregnancies. Preeclampsia was diagnosed using American College of Obstetricians and Gynecologists criteria and identified with International Classification of Diseases-9 coding. Early GWG z -score was modeled as a three-level categorical variable (≤ − 1 standard deviation [SD], 0, 3 +1 SD), where −1 to +1 was the referent group. We estimated risk differences and 95% confidence intervals (CIs) via marginal standardization. Results  We included 1,693 dichorionic twin pregnancies in the cohort. In adjusted analysis, the incidence of preeclampsia increased with increasing early GWG among women with normal BMI. Women with normal BMI and a GWG z -score < − 1 (equivalent to 2.6 kg by 20 weeks) had 2.5 fewer cases of preeclampsia per 100 births (95% CI: −4.7 to − 0.3) compared with the referent; those with GWG z -score > +1 (equivalent to gaining 9.8 kg by 20 weeks) had 2.8 more cases of preeclampsia per 100 (95 % CI: 0.1–5.5) compared with the referent. In adjusted analyses, early GWG had minimal impact on the risk of preeclampsia in women with overweight or obesity. Conclusion  GWG of 2.6 kg or less by 20 weeks was associated with a decreased risk of preeclampsia among women pregnant with dichorionic twins and normal prepregnancy BMI. Current GWG guidelines focus on optimizing fetal weight and gestational length. Our findings demonstrate the importance of considering other outcomes when making GWG recommendations for twin pregnancy. Key Points Early GWG decreased with increasing BMI category. Among women with normal weight, as early GWG increased so did the risk of preeclampsia. There was no association between early GWG and preeclampsia among women with overweight or obesity.