Abstract
BackgroundMetformin use in pregnancy is controversial because metformin crosses the placenta and the safety on the fetus has not been well-established. This retrospective study aimed to compare pregnancy outcomes in women with preexisting type 2 diabetes receiving metformin or standard insulin treatment.MethodsThe cohort of this population-based study includes women of age 20–44 years with preexisting type 2 diabetes and singleton pregnancies in Taiwan between 2003 and 2014. Subjects were classified into three mutually exclusive groups according to glucose-lowering treatments received before and after becoming pregnant: insulin group, switching group (metformin to insulin), and metformin group. A generalized estimating equation model adjusted for patient age, duration of type 2 diabetes, hypertension, hyperlipidemia, retinopathy, and aspirin use was used to estimate the adjusted odds ratio (aOR) and 95% confidence interval (CI) of adverse pregnancy outcomes.ResultsA total of 1166 pregnancies were identified in the insulin group (n = 222), the switching group (n = 318) and the metformin group (n = 626). The insulin group and the switching group had similar pregnancy outcomes for both the mother and fetus, including risk of primary cesarean section, pregnancy-related hypertension, preeclampsia, preterm birth (< 37 weeks), very preterm birth (< 32 weeks), low birth weight (< 2500 g), high birth weight (> 4000 g), large for gestational age, and congenital malformations. The metformin group had a lower risk of primary cesarean section (aOR = 0.57; 95% CI, 0.40–0.82) and congenital malformations (aOR, 0.51; 95% CI; 0.27–0.94) and similar risk for the other outcomes as compared with the insulin group.ConclusionsMetformin therapy was not associated with increased adverse pregnancy outcomes in women with type 2 diabetes as compared with standard insulin therapy.
Highlights
Metformin use in pregnancy is controversial because metformin crosses the placenta and the safety on the fetus has not been well-established
Maternal characteristics There were 1166 pregnancies included for the primary analysis based on case selection strategy, 222 were in the insulin group, 318 were in the switching group and 626 were in the metformin group
Compared with the insulin group, the switching group had a similar risk of primary cesarean section, pregnancy-related hypertension, preeclampsia, preterm birth, very preterm birth, low birth weight, high birth weight, large for gestational age, and congenital malformations
Summary
Data sources The Taiwan National Health Insurance (NHI) is a single-payer system established in 1995 that provides universal medical care coverage to over 99% of the Taiwan residents (approximately 23.5 million people), including all citizens and foreigners living in Taiwan for more than 6 months [18]. The Taiwan Birth Registry dataset was included in this study for the analysis of pregnancy outcomes. This data contains detailed birth characteristics of the mother and fetus, including method of delivery, gestational age, birth weight, Apgar score, congenital malformations, and stillbirth. Study outcomes Adverse pregnancy outcomes of the mother and fetus, including primary cesarean section, pregnancy-related hypertension, preeclampsia, preterm birth (< 37 weeks), very preterm birth (< 32 weeks), low birth weight (< 2500 g), high birth weight (> 4000 g), small for gestational age, large for gestational age, congenital malformations, Apgar score < 7 at 5 min and stillbirth were identified in the NHI and Birth Registry datasets. The level of statistical significance in this study was set at p < 0.05
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