Objective: Multifetal pregnancy reduction (MPR) is a technique developed to reduce the risks of a multifetal pregnancy. The objective of this article was to report the outcome of MPR in the largest single-center experience to date. Study Design: A computerized database was used to determine the outcome of 1000 consecutive cases patients undergoing transabdominal MPR between the years 1986 and 1999. Outcomes analyzed included pregnancy loss rates, preterm delivery rates, and mean birth weights. Results: The complete pregnancy loss rate was 5.9%, whereas the unintended pregnancy loss rate was 5.4%. The loss rate was 9.5% in the first 200 cases and remained stable at 4.5% to 6.0% over the next 800 cases. The loss rate was lowest with starting numbers of two fetuses (2.5%), remained stable for three, four, and five fetuses, and increased to 12.9% with starting numbers of six fetuses or greater. Loss rates were similar with a finishing number of one or two (3.5 % and 5.5%, respectively) but were highest for a finishing number of three (16.7%). Analysis of birth weights showed a linear decline with increasing starting and finishing numbers. Mean gestational age of delivery for finishing numbers of one, two, and three fetuses was 37.9, 35.3, and 33.5 weeks. Conclusion: Unintended loss rates associated with MPR have stabilized at 5.4%. Loss rates are highest with starting numbers of six or more fetuses, but did not differ for starting numbers of three, four, or five fetuses. Gestational age of delivery for finishing numbers of one, two, and three fetuses are similar to that of nonreduced pregnancies. (Am J Obstet Gynecol 2002;187:1163-7.)