['To determine the association of preterm birth with antimüllerian hormone (AMH) levels both in isolation and in combination with other markers of fetoplacental health commonly measured during integrated prenatal screening (IPS) for aneuploidy.', 'Retrospective case-control study.', 'Not applicable.', "Pregnant women in Iowa who elected to undergo IPS and who subsequently delivered in Iowa, including women giving birth at <37 weeks' gestation and controls who delivered at ≥37 weeks' gestation.", 'None.', 'Probability of a preterm birth.', 'Second trimester AMH levels were not associated with preterm birth, either independently or after controlling for other markers of fetoplacental health. The AMH difference was not associated with preterm birth when modeled alone, but a statistically significant association was found after adjusting for maternal serum α-fetoprotein (MSAFP) and maternal weight change between the first and second trimesters. After stratifying the model by MSAFP level, most of the risk for preterm birth was identified in women with an MSAFP >1 multiple of the median and who had a stable or rising AMH level in early pregnancy.'] Are changes in antimüllerian hormone levels in early pregnancy associated with preterm birth?