Body Weight-Related Parameters in Pregnancies Complicated by Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis with Maternal and Perinatal Outcome Mapping

Background: Type 2 diabetes mellitus (T2DM) in pregnancy is increasingly recognized as a high-risk metabolic condition, frequently accompanied by overweight, obesity, insulin resistance, and adverse maternal and neonatal outcomes. This systematic review and meta-analysis aimed to evaluate body weight-related parameters in pregnancies complicated by T2DM compared with those in non-T2DM control groups. Methods: A systematic search of PubMed, Scopus, and Web of Science was conducted up to 19 August 2025. Original studies reporting body weight, body mass index (BMI), or gestational weight gain (GWG) in pregnant women with T2DM and different control groups were included. Data were synthesized using standardized mean differences (SMDs) with fixed or random-effects models. Maternal, metabolic, delivery, and neonatal outcomes were summarized descriptively. Results: Eighty-seven studies were included in the systematic review and seventy-two were included in the meta-analysis. Pregnant women with T2DM had significantly higher pre-pregnancy body weight and first-trimester body weight than normoglycemic and T1DM controls. Pre-pregnancy BMI was also significantly higher in T2DM pregnancies compared with normoglycemic, T1DM, and gestational diabetes controls. In contrast, GWG did not differ significantly between T2DM and normoglycemic or gestational diabetes pregnancies, while it was significantly lower in T2DM than in type 1 diabetes pregnancies. Adverse maternal and neonatal outcomes, including hypertensive disorders, preterm delivery, fetal growth abnormalities, macrosomia, congenital anomalies, and fetal/neonatal loss, were frequently reported across the included studies. Conclusions: Pregnancies complicated by T2DM are characterized by an unfavorable preconception anthropometric profile. The contrasting patterns across diabetes types suggest different periods for weight-related care: preconception weight optimization appears particularly relevant in T2DM, whereas the higher gestational weight gain observed in T1DM relative to T2DM supports individualized monitoring of gestational weight trajectories during pregnancy. These strategies should be incorporated into comprehensive preconception and antenatal care alongside glycemic optimization and assessment of diabetes-related complications.