- Metformin use in pregnancy by women with type 2 diabetes (T2D) does not appear to raise risk for adverse pregnancy outcomes compared with insulin therapy.
Why this matters
- Metformin freely crosses the placenta, with fetal concentrations reaching those of the mother.
- Some (not all) guidelines advise switching from metformin to insulin at pregnancy onset.
- Primary analysis included 1166 pregnancies from the national Taiwanese database, including 222 on insulin (reference), 626 on metformin, and 318 switched from metformin to insulin at pregnancy onset.
- Adjustments made for age, T2D duration, hypertension, hyperlipidemia, retinopathy, and aspirin use.
- Funding: Chang Gung Memorial Hospital, Linkou, Taiwan.
- Compared with the insulin group, no significant differences were found for the switching group for risks for primary cesarean delivery, pregnancy-related hypertension, preeclampsia, birth at 4000 g, large for gestational age, or congenital malformations.
- The metformin group had lower risk for primary cesarean delivery (OR, 0.57; 95% CI, 0.40-0.82; P=.002) and congenital malformations (OR, 0.51; 95% CI, 0.27-0.94; P=.032); all other rates were similar.
- Secondary analysis results were consistent with primary findings.
- Women using insulin may have had more baseline comorbidities.
- Long-term offspring outcomes were not assessed.
- Retrospective, based on diagnostic codes.
- Covariates such as glycemic control and BMI were missing.