PURPOSE: To quantify the contribution of in vitro fertilization (IVF) on changes in the rates of low birth weight (LBW), preterm delivery, very low birth weight, and multiple births during the past 3 years. METHODS: Data on IVF pregnancies from 1994 to 1996 within Alberta were reviewed. Population data were obtained from the Provincial notice of a live or stillbirth. RESULTS: The IVF component of increased LBW rate in the province was 17.8% for infants <2500 g and 43.5% for those born <1500 g. IVF accounted for 10.5% of the provincial rate increase in deliveries <37 weeks' gestation and 66.2% of those