OBJECTIVES: To determine whether women discharged from hospital < or = 72 hours after childbirth (early discharge) were at greater risk of developing symptoms of postnatal depression during the following six months than those discharged later (late discharge), their reasons for early discharge and their level of postnatal support. DESIGN AND SETTING: Population-based, prospective cohort study with questionnaires at Day 4, and at 8, 16 and 24 weeks postpartum, conducted at all birth sites in the Australian Capital Territory (ACT). PARTICIPANTS: Women resident in the ACT giving birth to a live baby from March to October 1997. MAIN OUTCOME MEASURE: A score > 12 on the Edinburgh Postnatal Depression Scale (EPDS). RESULTS: 1295 (70%) women consented to participate; 1193 (92%) were retained in the study to 24 weeks and, of these, 1182 returned all four questionnaires. Of the 1266 women for whom length-of-stay data were available, 467 (37%) were discharged early and 799 (63%) were discharged late. There were no significant differences between the proportion of women discharged early who ever scored > 12 on the EPDS during the six postpartum months and those discharged late (17% v. 20%), even after controlling for other risk factors (adjusted OR, 0.67; 95% CI, 0.44-1.01). Of women discharged early, 93% had at least one postnatal visit at home from a midwife and 81% were "very satisfied" with the care provided. Most women (96%) reported they had someone to help in practical ways. CONCLUSIONS: Women discharged early after childbirth do not have an increased risk of developing symptoms of postnatal depression during the following six months.