OBJECTIVE: This study was undertaken to determine proportions of very-low-birth-weight (VLBW) multiple birth infants receiving neonatal intensive care whose mothers received various types of infertility treatment and to evaluate infertility treatment-associated morbidity and mortality. STUDY DESIGN: Study infants were multiples with birth weight 401 to 1500 g cared for in Cincinnati neonatal intensive care units from January 1996 to December 2000. Data were obtained retrospectively from the National Institute for Child Health and Human Development Neonatal Research Network registry. Use of infertility treatment (in vitro fertilization, injection or oral ovulation, and intrauterine insemination) was determined by maternal interview or chart review. The generalized estimating equation approach to logistic regression was used. RESULTS: The study included 382 infants of 212 mothers: 201=spontaneous conception (53%), 93=in vitro fertilization (24%), 55=injection (14%), 15=oral (4%), and 18=intrauterine insemination (5%). Neither gestational age nor birth weight differed between groups. More female (58%, P=.003) and white infants (95%, P