Abstract
AIM: Type 2 diabetes (T2D) in pregnancy is increasingly common and associated with suboptimal outcomes for these women and their children. We aimed to synthesize observational evidence on associations of modifiable preconception, pregnancy and postpartum risk factors with perinatal outcomes among women with pregestational T2D. METHODS: Searches were conducted in six databases (September 2023). Observational studies among women with pregestational T2D were included if they reported associations of modifiable risk factors with maternal and/or child outcomes. Screening, data extraction and quality assessments were conducted by two reviewers. Findings were synthesized through random effects meta-analysis or narrative synthesis when results were too few or heterogeneous to pool. RESULTS: Searches identified 15,578 results; 58 studies were included. Meta-analysis showed excessive gestational weight gain (GWG) was associated with large for gestational age (LGA) (OR 2.39, 95%CI 1.74-3.29) but not small for gestational age (SGA). Meta-analysis demonstrated no associations between preconception care or metformin use with adverse pregnancy, birth and neonatal outcomes. However, narrative synthesis showed preconception care was associated with increased use of folic acid and vitamin D, and reduced GWG. Further narrative synthesis findings showed that higher BMI was associated with multiple suboptimal pregnancy, birth and neonatal outcomes. Excessive GWG was associated with increased insulin requirements and increased likelihood of neonatal hypoglycaemia. The use of metformin/oral hypoglycaemic medications was associated with reduced GWG and fewer caesarean deliveries. There was mixed or no evidence of association for other reported exposures and outcomes. CONCLUSION: Based on observational evidence, increasing access to preconception care could be beneficial to optimize maternal nutrition and weight-related outcomes, and addressing obesity and GWG has the potential to improve maternal and neonatal outcomes in pregnancies affected by T2D.