Historically, in order to compensate low rates for implantation of individual embryos and achieve high pregnancy rates, multiple embryos have been transferred in the major IVF cases. As a consequence, IVF carried a substantial risk of multiple pregnancy and its associated adverse effects on mothers and children.

The American Society for Reproductive Medicine (ASRM) reports that in the year 2000 more than two-thirds of all IVF transfer procedures in the United States were performed with the use of three and more embryos. With a steady improvement of the implantation rates ASRM has published its Practice Guidelines (1998) that have been periodically revised and adjusted. With the release of these guidelines the frequency of the transfer of three or more embryos has declined distinctly.

The policy of the European Society of Human Reproduction and Embryology (ESHRE) on reducing the incidence of multiple pregnancies in IVF was firstly set out in its position paper ?On Good Clinical Treatment in Assisted Reproduction? (2008). This document advocates an elective single embryo transfer (SET) in selected groups of patients as the only effective means of lowering the rate of multiple pregnancies and negative pregnancy outcomes after in-vitro fertilisation. SET may namely be defined as an embryo transfer in which more than one high quality embryo exists, but it was decided to transfer only one embryo.

Nonetheless, ESHRE also pointed out that that such SET policies can only be applied successfully in combination with high quality embryo selection and good cryopreservation programs. Recent observational studies demonstrate relatively poor results in cases, where only one embryo was available, and of good outcome, when a single embryo was elected for transfer. SET is most appropriate for those with a good prognosis: age less than 35, first or second treatment cycle, prior successful IVF and recipients of embryos from donated eggs.

In course of the latest prospective study of UK Human Fertilisation and Embryology Authority data 124,148 IVF cycles (which yielded 33,514 live births) have been investigated in order to determine if live birth outcomes varied by the number of embryos transferred in relation to maternal age. The study findings published on January 12, 2012 in the world?s leading general medicine journal ?The Lancet? strongly confirmed that the transfer of three or more embryos at any age should be discouraged. The decision to transfer one or two embryos should be based on prognostic indicators, such as age, number of previous IVF/ICSI cycles and embryo quality.

According to the aforementioned ESHRE?s position paper a two embryo transfer (DET) policy is now common in most European countries.

In Ukraine these trends are reflected the ?Instruction on Procedures for Assisted Reproductive Technologies?, adopted by the Order of the Ministry of Health of Ukraine No. 771 of 12/23/2008. Its Section 3.6 namely stipulates that it is recommended to transfer no more than 1-2 embryos in the course of IVF procedure. When low rate of embryo implantation is anticipated, it should be possible to transfer more embryos, but not exceeding 3 embryos when a woman consents thereon. Subject to the woman?s written consent a selective single embryo transfer combined with cryopreservation of the remaining viable embryos for the later use can be performed.

Thereby the ?Instruction on Procedures for Assisted Reproductive Technologies in Ukraine? allows embryo transfer at different stages, from cleavage stage (after only three days in laboratory) to the blastocyst stage (when embryos are cultured for 5-6 days until they have 60-100 cells).