A Systematic Review Supporting the Clinical Practice Guidelines on the Management of Preexisting Diabetes and Pregnancy.

Context: Women with preexisting diabetes mellitus (PDM) are at increased risk of pregnancy-related complications.

Objective: To summarize the available supporting evidence for the Endocrine Society guidelines about management of PDM in pregnancy.

Data Sources: MEDLINE, EMBASE, Scopus, and other sources through February 2025.

Study Selection: Studies were selected by pairs of independent reviewers.

Data Extraction: Data were extracted by pairs of independent reviewers.

Data Synthesis: We included 17 studies. Meta-analysis showed no significant difference between hybrid closed-loop insulin pump (HCL) and standard of care regarding time in range (TIR), time above range (TAR), and time below range (TBR). HCL had better overnight TIR and TBR. For women with type 2 diabetes mellitus (T2DM), intermittent use of continuous glucose monitoring (CGM) was not associated with a significant change in the risk of large for gestational age (LGA) neonates (2 randomized controlled trials [RCTs], 102 patients). Adding metformin to insulin was associated with a lower risk of LGA (2 RCTs, 1126 patients). Three retrospective studies (1724 patients) suggested increased neonatal complications when delivery was induced before 39 weeks of gestation (particularly before 38 weeks) in women with preexisting type 1 (T1DM) and T2DM, although this evidence was subject to likely confounding. One retrospective study showed no increase in neonatal complications with periconceptional exposure to glucagon-like peptide-1 receptor agonists. We could not identify comparative studies assessing a screening question about the possibility of pregnancy or a carbohydrate restrictive diet.

Conclusion: This systematic review addresses various aspects of managing PDM in pregnancy and will support the development of the Endocrine Society guidelines.