LAUSR

To examine trends in rates of preterm birth by race and plurality; to evaluate the association between race, plurality, and phenotypes of preterm birth. Temporal trends analyses for preterm birth by race and plurality were performed for the years 1971–2018. Adjusted logistic regression models were utilized to evaluate the association between race, plurality, and phenotypes of preterm birth. We observed that 1105,266 (0.7%), 1901,604 (1.2%), and 14,769,746 (9.3%) births belonged to extreme preterm, very preterm, and moderate-to-late preterm categories, respectively. We also observed that the risk of extreme preterm (RR: 2.69, 95% CI: 2.642–2.75) was highest for Black mothers as compared to White mothers. Over the study period, preterm births disproportionately impacted Black mothers as well as pregnancies of higher plurality. With the persistence of racial disparities and growing trend of delayed childbearing and multiple pregnancies, targeted intervention is necessitated toward these vulnerable subgroups.