Background: Single embryo transfer (SET) is the most effective way of reducing multiple pregnancy rates associated with assisted reproductive technology (ART). Despite published evidence suggesting that the judicious use of elective SET can lead to near-elimination of multiples without compromising cumulative live birth rates, the uptake of this strategy has been variable.
Methods: Medline, EMBASE and the Cochrane Database of Systematic Reviews (1978-2010) were searched using appropriate MeSH headings. Leading fertility journals along with appropriate cross references were hand searched and information retrieved from national ART registers and websites of national fertility societies in order to determine current rates of SET. We explored social, economic and clinical factors determining the uptake of SET.
Results: It was not possible to distinguish elective from non-elective SET from national ART reports. Data from 31 countries suggest that there has been a gradual increase in SET rates over a 3 year period (2003-2005) but major geographical differences were noted. SET rates are highest in Sweden (69.4%) but are as low as 2.8% in the USA. Access to public funding for ART, availability of good cryopreservation facilities and legislation appear to be the most important reasons favouring the uptake of SET. Personal choice plays a significant role as many subfertile couples have a strong preference for twins. Awareness that double embryo transfer (DET) increases live birth per fresh treatment cycle, inability to accurately identify women at high risk for twins and limitations of existing embryos selection criteria are barriers to a wider acceptance of SET.
Conclusions: The current variation in the uptake of elective SET is likely to persist until there are major changes in the way ART is viewed, funded and legislated.