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Multiple pregnancy rate and embryo number transferred during in vitro fertilization
C W Elsner1, M J Tucker, C L Sweitzer
1Reproductive Biology Associates, Atlanta, GA 30342, USA.
Objective:
Our goal was to achieve a good pregnancy rate after in vitro fertilization; more than one embryo, if available, is transferred to the uterine cavity. This is a recognition of the low implantation rates of embryos from in vitro fertilization. A consequence of this can be high-order multiple implantation with obstetric complications.
Study Design:
Retrospectively, we reviewed 42 months' in vitro fertilization experience; we related the number of embryos transferred and the pregnancy outcome. During this period 2173 fresh and frozen-thawed embryo transfers were performed. One to six embryos were transferred to women 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 related 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 reflects the number of embryos that implant per total transferred, was not significantly different in any one group, except in older women in whom more than one embryo was transferred. Whereas greater numbers of embryos (more than three) were transferred in couples with a poorer prognosis for successful in vitro fertilization (e.g., older women [> 36 years old], previous failure of in vitro fertilization, poor embryo quality, or severe male factor causing infertility), there still remained a significant trend toward a higher pregnancy rate when more embryos were transferred. The embryonic implantation rate did not decline in the poorer-prognosis groups (more than three embryos transferred), yet the multiple pregnancy rate was increased. Technologic procedures such as embryo biopsy for aneuploidy screening are proposed as one means to reduce embryo numbers transferred without decreasing the overall pregnancy rate.