This study evaluated the effect of multifetal pregnancy reduction on the incidence of small for gestational age (SGA) and discordance in reduced versus nonreduced twins and differences in placental pathology. A computerized ultrasound database was used to identify diamniotic-dichorionic twins who delivered at our institution. Reduced (n = 36) versus nonreduced twins (n = 243) were compared for differences in rates of SGA and discordancy (>or= 20%.) The groups were compared for differences in maternal and neonatal characteristics, as well as differences in placental pathology. Chi-square tests were used to compare differences in means. Stepwise logistic regression was used to adjust for potential confounders including placental pathology. The rate of SGA in either twin A or B remained nonsignificant after adjustment for the use of assisted reproductive technology and gestational age at delivery in the stepwise logistic model (odds ratio, 1.7 95%; confidence interval, 0.5, 5.2). The average discordance at delivery was 12.4% in reduced versus 11.4% in the nonreduced twins ( P = 0.54). We found no overall differences in placental pathology between the two groups. Reduced and nonreduced twins have no significant differences in SGA fetuses, growth discordancy, or placental pathology.