Comparison of singleton and multiple pregnancies in in vitro fertilization (IVF) and embryo transfer (ET).

The purpose of this study was to analyze factors associated with multiple gestations in IVF-ET. Twenty-seven multiple gestations conceived following IVF-ET resulted in the delivery of 20 sets of twins and three sets of triplets. One quadruplet pregnancy was terminated due to heavy bleeding. There were four "vanishing sacs," two of which resulted in a twin pregnancy and two in singletons. These were compared to 88 singleton IVF-ET gestations. The only significant difference found was the higher numbers of embryos transferred in the multiple gestation group. No difference was found between the two groups in diagnosis, stimulation protocol, estradiol, response, number of eggs, fertilization, and cleavage rate. Maternal age was younger in the multiple-gestation group, though not statistically significant. It is thus suggested that limitation of the number of embryos transferred is the only means to reduce the incidence of multiple gestations in IVF-ET.