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.