MULTIPLE PREGNANCY RATE AND EMBRYO NUMBER TRANSFERRED DURING IN-VITROFERTILIZATION

OBJECTIVE: Our goal was to achieve a goad pregnancy rate after in vitr o fertilization; more than one embryo, if available, is transferred to the uterine cavity. This is a recognition of the low implantation rat es of embryos from in vitro fertilization. a consequence of this can b e high-order multiple implantation with obstetric complications. STUDY DESIGN: Retrospectively, we reviewed 42 months' in vitro fertilizatio n experience; we related the number of embryos transferred and the pre gnancy outcome. During this period 2173 fresh and frozen-thawed embryo transfers were performed. One to six embryos were transferred to wome n whose average age was 34.4 years (range 21 to 49). RESULTS: A total of 734 delivered pregnancies (33.8% per embryo transfer) was analyzed according to whether they were single or multiple, and this was relate d to the original number of embryos transferred. The overall multiple pregnancy rate was 31.3% (24.7% twins, 5.8% triplets, 0.8% quadruplets ). CONCLUSIONS: There was a trend toward a higher pregnancy rate with more embryos transferred. The embryonic implantation rate, which refle cts the number of embryos that implant per total transferred, was not significantly different in any one group, except in older women in who m more than one embryo was transferred. Whereas greater numbers of emb ryos (more than three) were transferred in couples with a poorer progn osis for successful in vitro fertilization (e.g., older women [>36 yea rs old], previous failure of in vitro fertilization, poor embryo quali ty, or severe male factor causing infertility), there still remained a significant trend toward a higher pregnancy rate when more embryos we re transferred. The embryonic implantation rate did not decline in the poorer-prognosis groups (more than three embryos transferred), yet th e multiple pregnancy rate was increased. Technologic procedures such a s embryo biopsy for aneuploidy screening are proposed as one means to reduce embryo numbers transferred without decreasing the overall pregn ancy rate.