Since the first pregnancy after in vitro fertilization and embryo transfer (IVF-ET) over a million pregnancies have been achieved worldwide by IVF and its modifications. On a per cycle basis, the results of IVF are similar to the fecundability of natural conception cycles in the general population. The cumulative success rate is higher when IVF is attempted on a repetitive basis. Pregnancy rates have consistently improved over time. By 2002, the delivery rate per retrieval was 32%. However, the incidence of twins and high order multiple pregnancies (ie. triplets or more) has risen over the past two decades. From 1980 to 1997, the annual number of live born babies from twin gestations rose 52%,while the number of high order gestations increased 404%. This rise was mainly due to increased use offertility drugs for ovulation induction, superovulation, and IVF. Compared to natural ovulation and conception, IVF increases the chance of having twins 20-fold and triplets/quadruplets 400%. A number of studies have reported an increase in the adverse perinatal outcome of pregnancies obtained with IVF-ET. Multiple gestations are at increased risk of fetal, neonatal, complications, as well as complete pregnancy loss, when compared to singleton pregnancies. Neonatal complications are primarily the result of preterm delivery. Several strategies attempting to control the frequency of high order multiples have been implemented. The overriding aim of these strategies is to transfer fewer embryos of higher quality to maximize the pregnancy rate and to minimize the risk of high order multiple gestation.Utilization of single embryo transfer will likely increase as method of predicting embryo viability and to reduce high order pregnancy mounts.