The likelihood of U.S. women giving birth to three or more babies from a single pregnancy has decreased in the last 15 years after rising in previous decades. The reversal coincides with changes in how in vitro fertilization, or IVF, is done, researchers report in the Dec. 5 New England Journal of Medicine.
In IVF, doctors implant embryos — often more than one — into a woman’s uterus. In the late 1990s, three-fourths of IVF procedures in the United States transferred three or more embryos at once, report Aniket Kulkarni of the Centers for Disease Control and Prevention in Atlanta and colleagues.
The likelihood of having three or more babies after a single pregnancy was five times as high in 1998 as in 1971, according to the analysis. The increase traces to IVF, other fertility treatments and more women giving birth at an older age.
Since 1998, in part due to changes in IVF procedures, the United States saw a 29 percent decline in births of three or more babies. Only about one-fourth of U.S. procedures today transfer more than two embryos, the scientists find. From 1998 to 2011, the number of IVF-assisted births resulting in three or more babies dropped from more than 140 per 1,000 IVF pregnancies to 30 per 1,000, they report.
A.D. Kulkarni et al. Fertility treatments and multiple births in the United States. New England Journal of Medicine. Vol. 369, December 5, 2013, p. 2218. doi: 10.1056/NEJMoa1301467.
N. Seppa. Medical Nobel goes to developer of IVF. Science News Online, October 4, 2010.