Efficacy and Adverse Side Effects of Two Forms of Iron in Pregnancy

This two-arm, double-blind randomized clinical trial will recruit 208 generally healthy, low-risk pregnant individuals aged 19-42 years living in Vancouver, Canada. Participants will be randomized to receive one of two forms of iron (ferrous fumarate or ferrous bisglycinate) in addition to a prenatal multivitamin (without iron) daily during their pregnancy until delivery, with optional continuation until \~4 weeks postpartum for breastmilk sample collection. Blood samples will be taken at baseline and again at \~37 weeks gestation to assess how different forms of iron impact body iron stores. Rectal swabs will also be taken at baseline and \~37 weeks gestation to detect presence of harmful bacteria in the gut and quantify their abundance. This research will inform more specific guidelines for optimal iron supplementation practices for the prevention and treatment of iron deficiency for both mother and baby.