From the Guidelines
Women with Polycystic Ovary Syndrome (PCOS) taking metformin should discontinue the medication by the end of the first trimester, as recommended by the latest standards of care in diabetes-2023 1. This recommendation is based on the potential risks associated with metformin use during pregnancy, particularly the fact that it crosses the placenta to the fetus. When considering gestational diabetes mellitus (GDM) screening, it is essential to prioritize accurate test results to ensure proper diagnosis and management of GDM during pregnancy. Key points to consider include:
- Metformin improves insulin sensitivity and lowers blood glucose levels, which could mask the presence of GDM during screening tests like the oral glucose tolerance test (OGTT) 1.
- The American Diabetes Association recommends that metformin be discontinued by the end of the first trimester when used to treat PCOS and induce ovulation 1.
- Insulin is the preferred medication for treating hyperglycemia in GDM, as metformin and other oral glucose-lowering medications lack long-term safety data or cross the placenta to the fetus 1.
- The risks associated with untreated GDM, such as macrosomia, birth injuries, and increased risk of cesarean delivery, emphasize the importance of accurate diagnosis and management 1. In clinical practice, the temporary discontinuation of metformin before GDM screening should be discussed with the healthcare provider, taking into account individual circumstances and medical history. However, based on the latest evidence, discontinuing metformin by the end of the first trimester is the recommended approach 1.
From the Research
Discontinuation of Metformin for PCOS Prior to GDM Screening
- The decision to discontinue metformin for Polycystic Ovary Syndrome (PCOS) prior to completing an early Gestational Diabetes Mellitus (GDM) screening during pregnancy is a complex one, with various studies providing insights into the effects of metformin on pregnancy outcomes 2, 3, 4, 5, 6.
- A study published in 2008 found that continuous use of metformin during pregnancy significantly reduced the rate of miscarriage, gestational diabetes requiring insulin treatment, and fetal growth restriction in women with PCOS 2.
- However, a meta-analysis of randomized controlled trials published in 2020 found that metformin does not contribute to averting the GDM outcome in women at high risk when initiated in pregnancy 3.
- Another study published in 2013 found that metformin reduces the risk of gestational diabetes in women with PCOS, but the mechanisms of action of this drug during pregnancy are not fully understood 4.
- A systematic review published in 2013 found that metformin appears to be effective and safe for the treatment of gestational diabetes mellitus (GDM), particularly for overweight or obese women, and reduces the rates of early pregnancy loss and preterm labor in women with PCOS 5.
- A recent update published in 2025 suggests that continuing metformin to the end of the 1st trimester at an effective dose may help to reduce the rate of miscarriages, and that metformin is generally safe for the mother and neonate 6.
Considerations for Discontinuation
- The evidence suggests that metformin may have benefits for women with PCOS, including reducing the risk of gestational diabetes and improving pregnancy outcomes 2, 4, 5, 6.
- However, the decision to discontinue metformin prior to GDM screening should be made on a case-by-case basis, taking into account individual patient factors and clinical judgment 5, 6.
- Further research is needed to define the optimal dosage and times to initiate and discontinue metformin in women with PCOS who achieve pregnancy 6.