Metformin appears safe during pregnancy for women with T2D

  • Lin SF & al.
  • BMC Pregnancy Childbirth
  • 04.09.2020

  • von Miriam Tucker
  • Clinical Essentials
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Takeaway

  • 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.

Study design

  • 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.

Key results

  • 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.

Limitations

  • 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.