Your San Diego fertility center: Reproductive Sciences Center & Genetics Institute

where babies come from...

Gestational Surrogacy Enhances Implantation Rates In Egg Donation Cases

This research at the American Society for Reproductive Medicine (ASRM), San Antonio, Texas, 2003.

CA Adams, LS Anderson and SH Wood. Reproductive Sciences Center, La Jolla, CA, USA.

Objective: Evidence derived from egg donation studies suggests that oocyte quality may be the most important factor determining implantation failure and pregnancy loss. The potential role of a uterine factor, other than in cases with detectable uterine pathology, is more controversial. The aim of this study was to assess the contribution of a possible uterine factor on implantation and pregnancy loss by comparing embryo transfers into surrogate and non-surrogate recipients. By considering only egg donation cycles, the confounding effects of oocyte quality were controlled.

Design: A retrospective analysis of IVF/ICSI fresh and frozen (FET) egg donation cases performed at one center over a five-year period, 1997-2002. Women with detectable uterine pathology were excluded.

Materials and Methods: A total of 172 fresh cases (53 IVF and 43 ICSI non-surrogate, and 56 IVF and 20 ICSI surrogate) and 64 frozen transfers (37 non-surrogate and 27 surrogate) were evaluated. Surrogate and non-surrogate cycles were compared with respect to age of oocyte donor (for FET cycles, age when embryos were frozen), age of embryo recipient (surrogate/patient), number of embryos transferred, and implantation, clinical pregnancy and miscarriage rates using chi-square or unpaired t-tests, as appropriate, for statistical analysis. The same clinical protocol was used to prepare the endometrium in both groups.

Results: There were no significant differences in the number of eggs retrieved, fertilization rate or number of embryos transferred between the surrogate and non-surrogate groups. Implantation rates following fresh embryo transfers were significantly higher for surrogates (42%) than for non-surrogates (33%, p<. 05). Surrogates also had a higher implantation rate (28%) than non-surrogates (15%, p<. 01) in FET cycles. Although there were no significant differences in clinical pregnancy rates between the surrogate (73%) and non-surrogate (65%) groups for fresh embryo transfer cycles, surrogates had a significantly higher pregnancy rate (74%) than non-surrogates (43%, p<. 025) in FET cycles. There were no significant differences in miscarriage rates between these groups.

Conclusions: Implantation rates are enhanced in fresh and frozen egg donation cases using gestational surrogates as compared to non-surrogates. This increase in implantation rates in surrogates is seen in both male factor and non-male factor cases. The lower clinical pregnancy rates seen with non-surrogates in FET cycles may result from the transfer of embryos that remain after the highest quality have been transferred in fresh cycles. This data suggests that, in addition to the previously reported effects of oocyte quality, a uterine factor may contribute to implantation failure, and it supports the use of a gestational surrogate for patients with repeated pregnancy failure using egg donation.