The optimal number of embryos to be transferred in shared oocyte donation: walking the thin line between low pregnancy rates and multiple pregnancies.

There has been growing concern about the number of multiple gestations resulting from assisted reproductive technologies. For in-vitro fertilization (IVF), there are guidelines concerning the number of embryos to be transferred. In oocyte donation, however, there is a paucity of studies addressing this issue and common practice is extrapolated from standard IVF procedures. This may not be correct since endometrial receptivity has been shown to be altered in oocyte donation. Thus the purpose of this study was to assess the optimal number of embryos to be transferred in oocyte donation. The study population included 254 patients with ovarian failure who underwent a total of 601 embryo transfers in a single shared oocyte donation programme. Pregnancy rates (PRs), multiple pregnancies, triplet pregnancy rates, and implantation rates were evaluated according to the number of embryos transferred. A significant linear increase in PRs was noted with the increasing number of embryos transferred up to five (11.1% for one embryo, 36.7% for five embryos). Multiple pregnancies increased significantly from 15.8% for two embryos transferred, to 44.4% for five embryos. The rate of triplet pregnancies also increased from 2.7% for three embryos transferred, to 8.3% for five embryos. Optimization of the number of embryos to be transferred is discussed.