Housing instability is an understudied social condition that may be a severe stressor during pregnancy. Aims of this study are to identify correlates of housing instability and to explore the association between housing instability and birth weight among pregnant teens and young mothers. Participants included pregnant women ages 14-21 from seven community hospitals and health centers in New York City (N = 623). Data were collected via structured surveys during the second trimester of pregnancy (14 to 24 weeks gestation, M = 19.35, SD = 3.20). Birth weight was obtained through labor and delivery logs. Housing instability was operationalized as two or more moves within the past year. More than one in four (28.5 %) pregnant teens and young women in this sample reported housing instability. Women who reported housing instability were less likely to be enrolled in school, have parents as main source of financial support, live in a single-family home or apartment, or be food secure; they were more likely to smoke (all p < 0.05). After adjusting for important clinical, behavioral, and demographic factors typically associated with lower birth weight, housing instability remained a significant predictor of lower birth weight (B (SE) = -83.96(35.47), p = 0.018). Results highlight the importance of housing stability during pregnancy for infant health. Future interventions and policies should ensure that women are housing stable before, during, and after pregnancy.