Effect of metformin on fetal growth in women with gestational diabetes and pre-conception risk factors for fetal growth restriction: a retrospective, population-based cohort study

Fathima Minisha, Komal Rafique, Sawsan Al Obaidly, Najat Khenyab, Salwa Abu Yaqoub, Nader Aldewik, Hilal Al Rifai, Thomas Farrell

Background: Metformin is an alternative first-line medication for gestational diabetes (GDM) to improve compliance and maternal BMI. The impact of the medication on fetal development is unclear. This study examines the effect of metformin on fetal growth and peripartum outcomes. The hypothesis was that metformin use negatively impacts birthweight in women already at higher risk for intrauterine growth restriction (IUGR).

Interpretation of results: The use of metformin for the management of GDM in women having pre-existing risk factors for IUGR is significantly associated with decreased birthweight in preterm, higher odds of preterm birth, emergency cesarean, low birthweight and small for gestational age babies. The use of metformin in this group should be cautious, after balancing the improvement in maternal glycemia with the possible risk of IUGR and future health concerns in the offspring. Non-pharmacological methods and insulin should remain the preferred methods of choice to tackle GDM in this group.