OBJECTIVE: The goal was to examine the impact of birth at night, on the weekend, and during July or August (the first months of the academic year) and the impact of resident duty-hour restrictions on mortality and morbidity rates for very low birth weight infants. METHODS: Outcomes were analyzed for 11 137 infants with birth weights of 501 to 1250 g who were enrolled in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network registry in 2001-2005. Approximately one-half were born before the introduction of resident duty-hour restrictions in 2003. Follow-up assessments at 18 to 22 months were completed for 4508 infants. Mortality rate, short-term morbidities, and neurodevelopmental outcome were examined with respect to the timing of birth. RESULTS: There was no effect of the timing of birth on mortality rate and no impact on the risks of short-term morbidities except that the risk of retinopathy of prematurity (stage ≥2) was higher after the introduction of duty-hour restrictions and the risk of retinopathy of prematurity requiring operative treatment was lower for infants born during the late night than during the day. There was no impact of the timing of birth on neurodevelopmental outcome except that the risk of hearing impairment or death was slightly lower among infants born in July or August. CONCLUSION: In this network, the timing of birth had little effect on the risks of death and morbidity for very low birth weight infants, which suggests that staffing patterns were adequate to provide consistent care. Copyright © 2010 by the American Academy of Pediatrics.