This randomized controlled trial evaluates whether nightly vaginal micronized progesterone (400 mg) initiated before 12 weeks' gestation reduces the incidence of preeclampsia in low-risk pregnant individuals. Participants will be randomly assigned (1:1) to receive either vaginal progesterone through 16 weeks' gestation or routine prenatal care without progesterone. Maternal and neonatal outcomes-including development of preeclampsia, obstetric complications, gestational diabetes, preterm birth, and neonatal morbidity-will be collected via chart review. The study aims to determine whether early progesterone supplementation decreases the risk of preeclampsia.

Inclusion Criteria:

• Pregnant individuals receiving prenatal care at participating clinics
• <12 weeks gestation with a viable intrauterine pregnancy
• Age ≥18 years
• English-speaking

Exclusion Criteria:

• Unable or unwilling to self-administer vaginal progesterone
• Inability or unwillingness to provide informed consent