Determinants of multiple pregnancies in in vitro fertilization other than number of transferred embryos.

The aim of this study is to assess the many different parameters involved in the incidence of multiple pregnancies, such as maternal age, stimulation, endometrium, receptivity and the quality of the transferred embryos. During a 3.5 year period, 86 pregnancies were recorded in our IVF unit. A single gestational sac was identified by early ultrasonography in 67 patients, while in 19 others, multiple sacs were noted. Patient characteristics, treatment cycles and embryology results were similar in the two groups. When the number of transferred embryos was kept similar in both groups, EIR was found to be a valuable prognostic determinant for multiple pregnancies in IVF.