An in vitro fertilization technique that can avoid multiple births appears to be effective for women older than 35, according to researchers at the Stanford University School of Medicine.
More than half the women in a retrospective study became pregnant after undergoing the procedure, called a single blastocyst transfer, which transferred just one embryo into the womb.
Nearly 60 percent of IVF procedures in the United States are performed on women older than 35, and the study's senior author, Amin Milki, MD, believes the findings are good news for those women who wish to become pregnant with just one child.
"Although these results represent a selected group of patients, we believe that they should serve as encouragement to patients and providers who are considering single blastocyst transfer in the older IVF population," Milki and his co-authors noted in the study, which was recently published online in the journal Fertility and Sterility.
During the transfer procedure, an embryo is bathed in a culture of nutrients for five days until it reaches a developmental landmark known as the blastocyst stage. At that point, doctors are able to determine which embryos are most likely to thrive long term; they then transfer the best-quality ones into a woman's uterus.
The American Society for Reproductive Medicine currently recommends that doctors transfer two or more embryos into women older than 35, in an effort to maximize a patient's chance of becoming pregnant. This practice can lead to twins or higher-order multiples - as well as subsequent health risks - but Milki said this doesn't stop most patients from undergoing the procedure.
"Many patients would prefer not to have two babies at once," said Milki, professor of obstetrics and gynecology and director of Stanford's IVF program. "But because the success rate is higher when multiple embryos are transferred, women are willing to take the gamble."
In recent years, many reproductive specialists - especially those in Europe - have embraced single embryo transfer as a way to prevent multiple gestations. And data now exist showing the procedure's effectiveness among women of younger reproductive age.