IMPORTANCE: Iron deficiency is the leading cause of anemia during pregnancy. According to survey data from 1999 to 2006, overall estimated prevalence of iron deficiency during pregnancy is near 18% and increases across the 3 trimesters of pregnancy (from 6.9% to 14.3% to 28.4%). An estimated 5% of pregnant persons have iron deficiency anemia. OBJECTIVE: The US Preventive Services Task Force (USPSTF) commissioned a systematic review to evaluate the evidence on the benefits and harms of screening and supplementation for iron deficiency with and without anemia on maternal and infant health outcomes in asymptomatic pregnant persons. POPULATION: Asymptomatic pregnant adolescents and adults. EVIDENCE ASSESSMENT: The USPSTF concludes that the current evidence is insufficient, and the balance of benefits and harms of screening for iron deficiency and iron deficiency anemia in asymptomatic pregnant persons on maternal and infant health outcomes cannot be determined. The USPSTF also concludes that the current evidence is insufficient, and the balance of benefits and harms of iron supplementation in asymptomatic pregnant persons on maternal and infant health outcomes cannot be determined. RECOMMENDATION: The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for iron deficiency and iron deficiency anemia in pregnant persons to prevent adverse maternal and infant health outcomes. (I statement) The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of routine supplementation for iron deficiency and iron deficiency anemia in pregnant persons to prevent adverse maternal and infant health outcomes. (I statement).