[Elective single embryo transfer in assisted reproduction]

Abstract

Background: In Norway, assisted reproduction has been regulated by law since 1987, but the in vitro fertilization (IVF)-clinics are free to decide the number of embryos transferred. During the 1990ies, the number of embryos replaced was reduced from three to two. Triplets almost disappeared, but the twinning rate remained unchanged. According to the latest national data, 27.5 % of the deliveries following IVF and intracytoplasmic sperm injection (ICSI) in 2002 were multiple births. In our hospital, 23.9 % of the deliveries following IVF/ICSI in 2003 were multiple births. To reduce the multiple pregnancy rate, eSET was introduced as a routine in patients with a high probability to become pregnant in November 2004.

Material and methods: The results of eSET from the beginning of November 2004 until July 2005 are presented. All three inclusion criteria for eSET had to be fulfilled: 1) age <or= 35 years, 2) first or second treatment, 3) at least one top quality embryo.

Results and interpretation: 163 out of 644 treatment cycles fulfilled all three criteria for eSET. For 54 (33 %) of the treated women, the treatment has resulted in live births or ongoing pregnancies, compared to 23 % of the treatments with two transferred embryos. The overall pregnancy rate was only slightly decreased (32.4 %) compared to before implementation of eSET (34 %). In the eSET group, 60 % of the patients had embryos available for cryopreservation. The cumulative pregnancy rate per started treatment cycle is expected to increase when pregnancies following transfer of frozen-thawed embryos are included. The overall twinning rate was reduced to 18.1 %. It should be possible to reduce the twinning rate further by for example raising the age-limit for eSET. An optimal trade-off between cumulative ongoing pregnancy rate and twinning rate could more easily be obtained if the Norwegian IVF-clinics and authorities establish an eSET policy.