In in vitro fertilisation (IVF), transferring a single embryo into a woman does not lower her chances of getting pregnant a study suggests.

It is known that IVF and other assisted reproductive technologies increase the risk of multiple pregnancy. In IVF treatment, it had been a routine and cultural approach where women would have been transferred with 2-3 embryos most of the time. The new study suggests that since the technology has improved we may be able to transfer single embryos and still maintain high pregnancy rates. It is also possible that this way fewer women give birth to twins, with all the attendant health risks.

Multiple pregnancy increases risk to the mother and the babies. there is an increased risk of preterm birt and related defects for the babies. Mothers can suffer with diabetes and high blood pressure more often if thay have twins.

Succes rates with IVF have imroved significantly over the last decade which has helped increase births if single embryos are transferred in younger women. It is important however that these women selected for single embryo transfer are judged to have a good chance of getting pregnant, said Jessica Kresowik at the University of Iowa in Iowa City, who led the study.

"In the past, you did need to implant multiple embryos in order to maintain those pregnancy rates," Kresowik told Reuters Health of the study, published in the journal Fertility and Sterility, a reputable American Journal.

In the UK number of embryos to be transferred has always been under the jurisdictin of the Human Fertilisation and Embryology Authority (HFEA) and no more than three was allowed even in the earlier days. Dr. Kresowik added that before technology improved, doctors might have used six embryos at once, hoping that one would result in a pregnancy. According to the American Society for Reproductive Medicine, no more than two embryos should be transferred for women under 35.

Babies conceived through IVF account for just one percent of births each year, but IVF is responsible for 17 percent of twins, Kresowik added. This figure shows the risk IVF brings with respect to the incidence of multiple births. When single embryo transfer policies are applied carefully, the proportion of women with multiple births can drop from 35 percent to less than 18 percent.

"You really can move toward single-embryo transfer and have it give you great success rates, and really low multiple rates," she told Reuters Health. SOURCE: Reuters