https://www.selleckchem.com/products/au-15330.html Most screening tools identifying women with substance use are not validated, used once in pregnancy, and are not reflective of continued substance use. We hypothesized that serial early prenatal substance screening leads to decreased substance use by the end of pregnancy and improved outcomes. This is a retrospective cohort study of mothers and their infants between 1/2015 and 12/2017. A self-reported substance screening tool was administered on the first prenatal visit and subsequent visits until delivery. For analysis, mothers were divided into three groups based on the trimester of their first screen and adjusted for demographics and risk factors. Early first trimester screening resulted in 52% of mothers having ≥ 3 screens throughout pregnancy vs. 6% of mothers with late third trimester screens (p < 0.001). Compared to third trimester screening, there was a five-fold decrease of any substance use at second trimester, a seven-fold decrease at first trimester, and a nine-fold decrease for marijuana at first trimester. Compared to third trimester screening, there was a significant five-fold increase of negative maternal urine drug screen, 3 ½ -fold increase in well newborn diagnosis, and a five-fold increase of no infant morphine treatment at first trimester. We identified improved maternal and infant outcomes with serial early prenatal substance use screening. Early maternal substance use identification is crucial for immediate referral for prevention and treatment, and for social and community services. Further research is needed on universal serial early prenatal screenings. We identified improved maternal and infant outcomes with serial early prenatal substance use screening. Early maternal substance use identification is crucial for immediate referral for prevention and treatment, and for social and community services. Further research is needed on universal serial early prenatal screenings. While some medical