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Gestational Surrogacy Greatly Enhances Pregnancy and Implantation Rates in Both Fresh and Frozen Embryo Transfers.

This Research Presented at the Pacific Coast Fertility Society, La Costa, California, 1999.

CA Adams, LA Anderson, C Montgomery, B Hansen and SH Wood Reproductive Sciences Center, 4150 Regents Park Row, Suite 280, La Jolla, CA 92037

Objectives: Studies have indicated that gestational surrogacy results in high pregnancy rates; however, whether this is primarily due to differences in uterine receptivity or embryo quality is unclear. An evaluation of fresh and frozen embryo transfers in surrogate and non-surrogate IVF/ICSI cycles was undertaken to examine this issue. Design: A retrospective study of IVF/ICSI fresh and frozen embryo transfer (FET) cycles performed during a one year period was conducted. Surrogate and non-surrogate cycles were compared with respect to age of oocyte donor/patient (for FET cycles, age when embryos were frozen), age of embryo recipient (surrogate/patient), number of embryos transferred, quality of embryos transferred, clinical pregnancy rates and implantation rates. Results: A total of 163 cycles were evaluated and divided into four groups: (a) 113 fresh embryo transfers into non-surrogates, (b) 30 FETs into non-surrogates, (c) 10 fresh embryo transfers into surrogates and (d) 10 FETs into surrogates. As expected, surrogates were significantly younger (mean age 30 years) than the non-surrogates receiving embryos (mean=36 years; p<. 01); however there were no significant differences in the mean age of the recipients of fresh or frozen embryos in either of these groups. The mean age of oocyte donor/patient, number of embryos transferred, and quality of embryos transferred were not significantly different across these four groups. Clinical pregnancy rates for each group were as follows: (a) 59%, (b) 33%, (c) 90%, and (d) 70%. The implantation rates for each group were as follows: (a) 19%, (b) 13%, (c) 42%, and (d) 27%. Conclusions: Pregnancy and implantation rates are greatly enhanced in both fresh and frozen embryo transfer cycles utilizing gestational surrogates as compared to non-surrogates. Because the uterine environment into which embryos are transferred in fresh surrogate and non-surrogate cycles differ significantly, it is not possible to determine if the enhanced pregnancy rate seen is simply due to a more optimal surrogate uterine hormonal milieu. Since this confounding variable is eliminated in FET cycles, the markedly improved pregnancy rates noted in this type of cycle strongly suggests that other aspects of uterine receptivity play an important role in the enhanced implantation rate seen in surrogate cycles. It is possible that surrogacy may benefit patients with unexplained infertility who have failed multiple ART cycles.

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