OBJECTIVE: Our purpose was to evaluate the relationship between the approach to obstetric management and survival of extremely low-birth-weight infants. STUDY DESIGN: In this prospective observational study we evaluated 713 singleton births of infants weighing ≤1000 gm during 1 year at the 11 tertiary perinatal care centers of the National Institutes of Child Health and Human Development network of maternal-fetal medicine units. Major anomalies, extramural delivery, antepartum stillbirth, induced abortion, and gestational age <21 weeks were excluded. The obstetrician's opinion of viability and willingness to perform cesarean delivery in the event of fetal distress were ascertained from the medical record or interview when documentation was unclear. Grade 3 and 4 intraventricular hemorrhage, grade 3 and 4 retinopathy of prematurity, necrotizing enterocolitis requiring surgery, oxygen dependence at discharge or 120 days, and seizures were considered serious morbidity. Survival without serious morbidity was considered intact survival. Logistic regression was used to evaluate the influence of the approach to obstetric management, adjusted for birth weight, growth, gender, presentation, and ethnicity. RESULTS: Willingness to perform cesarean delivery was associated with increased likelihood of both survival (adjusted odds ratio 3.7, 95% confidence interval 2.3 to 6.0) and intact survival (adjusted odds ratio 1.8, 95% confidence interval 1.0 to 3.3). Willingness to intervene for fetal indications appeared to virtually eliminate intrapartum stillbirth and to reduce neonatal mortality. Below 800 gm or 26 weeks, however, willingness to perform cesarean delivery was linked to an increased chance of survival with serious morbidity. Although obstetricians were willing to intervene for fetal indications in most cases by 24 weeks, willingness to perform cesarean delivery was associated with twice the risk for serious morbidity at that gestational age. CONCLUSIONS: The approach to obstetric management significantly influences the outcome of extremely low-birth-weight infants. Above 800 gm or 26 weeks the obstetrician should usually be willing to perform cesarean delivery for fetal indications. Between 22 and 25 weeks willingness to intervene results in greater likelihood of both intact survival and survival with serious morbidity. In these cases patients and physicians should be aware of the impact of the approach to obstetric management and consider the likelihood of serious morbidity and mortality when formulating plans for delivery.