Hyperemesis Gravidarum Risk Reduction With Metformin

The goal of this clinical trial is to evaluate whether daily oral metformin extended-release (metformin-XR), taken prior to and in early pregnancy, can reduce the risk and severity of Hyperemesis Gravidarum (HG), a severe nausea and vomiting condition in pregnancy, in individuals aged 18-49 who have experienced HG in a previous pregnancy and are trying to conceive. Researchers also aim to better understand which individuals may respond well - or poorly - to metformin based on biological and clinical characteristics.

The main questions this study aims to answer are:

1. Is metformin-XR well-tolerated when taken by non-pregnant individuals who have had HG in a previous pregnancy and are currently trying to conceive? 2. How safe and tolerable is metformin-XR when taken at increasing doses over an 8-week titration period and continued through early pregnancy (or for up to 12 months after reaching maintenance dose if pregnancy does not occur)? 3. Among those who become pregnant during the study, does pre-pregnancy metformin-XR use reduce the risk of HG coming back and lower the severity of nausea and vomiting symptoms? 4. How does pre-pregnancy metformin-XR use affect pregnancy outcomes, postpartum health, and newborn health and development? 5. Are there specific genetic, biomarker, demographic, or clinical features that predict whether someone is likely to benefit from metformin-XR or experience side effects that lead them to stop taking it?

Researchers will compare a metformin treatment group to a survey-only group (comparator, no study drug) to see if metformin-XR is associated with improved outcomes, including reduced HG recurrence and better maternal and neonatal health indicators.

Participants will:

Complete online questionnaires before pregnancy, during early pregnancy, and postpartum

(Treatment group only) Take daily metformin-XR and attend three brief study visits

(Treatment group only) Undergo blood draws at specified timepoints to assess safety and biological response