Transferring a single embryo to a woman can result in a similar number of pregnancies as double embryo transfer, while at the same time reducing the risk of multiple births and the complications due to twin pregnancies, a scientist said today at the 20th annual conference of the European Society of Human Reproduction and Embryology.
Dr. Ann Thurin, from Sahlgrenska University Hospital, Göteborg, Sweden, told the conference that her research had in a large study shown that single embryo transfer (SET) could produce an acceptable pregnancy rate while lowering the incidence of multiple pregnancies.
Dr.Thurin and her team undertook a randomised double-blind study in 11 centres – five in Sweden, two in Norway, and four in Denmark. 661 patients under 36 years of age, who were undergoing a first or second IVF cycle, and who had at least two good quality embryos available for transfer or freezing were included. The patients were randomised into two groups; the first to receive a fresh SET and if there was no live birth, a subsequent frozen SET, and the second to a double embryo transfer (DET)
"The concept of 1+1 compared with a 2-embryo transfer has not been tried before", said Dr. Thurin, "and we were pleased to see that the women who had SET had an ongoing pregnancy rate nearly as high as those who had DET (39.7% versus 43.5%)."
There were no significant differences for other variables – the average age of the women at fresh transfer was 30.9 in the SET group and 30.8 in the DET group, and the number of good quality embryos available 4.6 in both groups.
"The only problem is that SET patients might need to go through one additional frozen cycle in order to have the same chance of pregnancy, but that is offset by the lower risks for mothers and children by avoiding multiple births", said Dr. Thurin. "However, the selection of the right embryo for SET is essential and a careful assessment needs to be undertaken before a choice is made. It is also important to have a well organised and functioning freezing programme, so that embryos that are surplus after SET can be properly preserved", she said.