Reducing the number of embryos transferred in Sweden-impact on delivery and multiple birth rates.

BACKGROUND Reduction of the number of embryos transferred has been introduced to decrease the multiple birth rates (MBRs) after IVF and the associated risks for the children. The aim of this report is to present the effect of two steps in reduction of the number of embryos transferred, when applied in the majority of the patients, on national data for delivery and MBR after IVF in Sweden. METHODS This observational study is based on annual reports from all IVF clinics in Sweden to the National Board of Health and Welfare for the time period 1991-2004. RESULTS The main finding is that despite a successive reduction in the number of embryos transferred, delivery rates were maintained at around 26% while MBR decreased dramatically, from about 35% to around 5%. The same pattern was noticed, independent of age, for all women below 40. In comparison with the USA, lower delivery and MBR were noted for Sweden whereas a higher 'birth per embryo transferred' was found. CONCLUSIONS Single embryo transfer (SET) results in satisfactory delivery rates and a dramatic decrease in the MBRs, also when applied on a broad scale. The experience from Sweden ought to encourage other countries to introduce SET more widely.