Use of 3 or More In Vitro Embryos Is Too Risky, Study Concludes About 40 percent of in vitro fertilizations in the United States involve the transfer of three or more embryos, and more than 20 percent of pregnancies from IVF procedures result in multiple births. The health risks and expenses of these pregnancies are enormous. Now a British study, published online Jan. 12 in The Lancet, has found that the number of live births does not increase with the transfer of more than two embryos, but that the risk of harm does. Researchers looked at 124,148 IVF procedures that resulted in 33,514 live births. Among all women, the transfer of two embryos resulted in more live births than the transfer of one. But in those under age 40, transferring three embryos produced a lower rate of live birth than transferring two. In older women, transferring three embryos instead of two made no difference in the rate. The transfer of three or more embryos in any age group, however, was associated with a significantly higher risk of complications, including preterm birth and low birth weight. Scott M. Nelson, an author of the study and the chairman of obstetrics at the University of Glasgow, said the United States was one of the few countries in which more than two embryos may still routinely be transferred. "The study clearly shows that transferring three or more is not beneficial," he said.