Associations of High BMI and Excessive Gestational Weight Gain With Pregnancy Outcomes in Women With Type 1 Diabetes: A Systematic Review and Meta-analysis

BACKGROUND The increased risk of pregnancy complications in type 1 diabetes is mainly attributed to maternal hyperglycemia. However, it is unclear whether other potentially modifiable factors also contribute to risk in this population. PURPOSE We sought to assess whether high BMI and excessive gestational weight gain (GWG) are associated with perinatal complications in type 1 diabetes. DATA SOURCES We searched Medline, Embase, PubMed, Scopus, Web of Science, and Cochrane databases to January 2024. STUDY SELECTION Studies examining associations between periconception BMI or GWG and perinatal complications in type 1 diabetes were included. DATA EXTRACTION We used a predesigned data extraction template to extract study data including year, country, sample size, participants’ characteristics, exposure, and outcomes. DATA SYNTHESIS We included 29 studies (18,965 pregnancies; 1978–2019) in the meta-analysis. A 1 kg/m2/1 kg increase in preconception BMI or GWG was associated with a 3% and 11% increase, respectively, in perinatal complications (BMI odds ratio [OR] 1.03 [95% CI 1.01–1.06]; GWG OR 1.11 [95% CI 1.04–1.18]). Preconception BMI ≥ 25 kg/m2 or excessive GWG was associated with a 22% and 50% increase, respectively, in perinatal complications (BMI OR 1.22 [95% CI 1.11–1.34]; GWG OR 1.50 [95% CI 1.31–1.73]). BMI was associated with congenital malformation, preeclampsia, and neonatal intensive care unit admission. Excessive GWG was associated with preeclampsia, cesarean delivery, large for gestational age, and macrosomia. LIMITATIONS Limitations included retrospective study design, variable measurement for exposures and outcomes, small number of studies for some outcomes, and no data from Asia and Africa. CONCLUSIONS Addressing maternal BMI prepregnancy and preventing excessive GWG should be key clinical priorities to improve outcomes in pregnant women with type 1 diabetes.