For women over 40 undergoing in vitro fertilization (IVF), transferring five embryos leads to the best outcomes, investigators report.

The Society for Assisted Reproductive Technology (SART) currently recommends that no more than five embryos be transferred in women over 40. “However, this isn’t based on very good data,” said Dr. Elizabeth Ginsburg.

To test the validity of the SART guidelines, Ginsburg, from the Brigham and Women’s Hospital Center For Reproductive Medicine, Boston, and colleagues evaluated and compared clinical outcomes when one to 11 embryos were transferred in women in this age group.

Specifically, of 863 transfers, 142 patients received exactly five embryos, 392 received fewer, and 329 received more than five embryos, according to the report in the medical journal Fertility and Sterility.

When fewer than five embryos were transferred, the overall pregnancy rate was 19 percent, and the live birth rate was 4percent. With five embryos, the pregnancy rate was 40 percent and the live birth rate was 23 percent.

With more than five, the overall rate was 47 percent, and the live birth rate was 22 percent - but the risks of multiple gestations rose.

“With more than five, you increase the number of multiple pregnancies, but you don’t increase the likelihood of a delivery,” Ginsburg pointed out.

“Triplets have a higher risk of all kinds of bad outcomes, and twins also have higher risks of prematurity,” she explained. “Women are also more likely to have diabetes and pregnancy complications with twins, especially if they’re over 40.”

So there is “good reason to stick with the SART recommendation, which is what is currently done in clinics,” Ginsburg concluded.

SOURCE: Fertility and Sterility, December 2005.