Elective transfer of one embryo results in an acceptable pregnancy rate and eliminates the risk of multiple birth

To avoid multiple pregnancies without compromising pregnancy rates (PR) is a challenge in assisted reproduction. We have compared pregnancy results am ong 74 elective one-embryo transfers (group 2) and 94 transfers where only one embryo was available (group 1), All the fresh embryo cycles during 1997 in two clinics in Helsinki were analysed, and cumulative PR among these co uples after frozen-thawed embryo transfers up to June 1998 were counted. In group 2, where at least two embryos were available for transfer, and only one was transferred on day 2 or 3, the PR per embryo transfer was 29.7%. In group 1, the PR per embryo transfer was 20.2%, In group 2, the cumulative PR after frozen-thawed embryo transfers was 47.3% per oocyte retrieval, Ove r the same time, 742 two-embryo transfers were carried out. The PR per embr yo transfer was 29.4% in these subjects, but 23.9% of these pregnancies wer e twins. The implantation rates, as well as the PR, were highest when the e mbryos were at the four- to five-cell stage on day 2 (35.8 versus 9.7% comp ared with the two- to three-cell stage, P < 0.001) or at the six- to eight- cell stage on day 3 (45.5%). The PR per embryo transfer was higher when a g rade 1 or 2 embryo was transferred compared with a grade three embryo (34.0 and 26.7% versus 8.8% respectively, P < 0.05). In women 35 years or younge r, the PR per elective one-embryo transfer was 32.8%, The corresponding fig ure in women older than 35 years was 18.8%. On the basis of these results, elective one-embryo transfer can be highly recommended, at least in subject s who are younger than 35 years of age, and who have grade one or grade two embryos available for transfer.