To characterise determinants of resident maternity leave and their effect on maternal and infant well-being. Among non-parents, to identify factors that influence the decision to delay childbearing STUDY DESIGN: In 2016, a survey was sent to female residents at a large academic medical centre on their experiences with maternity leave, the impact of personal and programme factors on length of leave, reasons for delaying childbearing and measures of well-being.Forty-four percent (214/481) of residents responded. Fifty (23%) residents were parents, and 25 (12%) took maternity leave during training. The average maternity leave length was 8.4 weeks and did not differ across programme type, size or programme director gender but was longer for programmes with fewer women than men. The most common self-reported determinant of leave was financial. Residents with 8 weeks of leave were less likely to have postpartum depression or burnout and more likely to breastfeed longer, perceive support from colleagues and programme directors, and be satisfied with resident parenthood. Among 104 non-parents who were married or partnered, 84 (81%) were delaying childbearing, citing busy work schedules, concern for burdening colleagues and finances.This study suggests that multiple aspects of resident wellbeing are associated with longer maternity leaves, yet finances and professional relationships hinder length of leave and lead to delayed childbearing. These issues could be addressed at a programme level with clear policies describing how work is redistributed during parental leave and at an institutional and state level through provision of paid family leave.