Number of multiple births from assisted reproduction decline because fewer embryos per cycle transplanted

Transplant News,  August 12, 2004  

• E-mail
• Print
• Link

Multiple births resulting from assisted reproduction technology are declining nationally because doctors are implanting fewer embryos per cycle, according to an analysis of US in vitro fertilization (IVF) data published in the April 15 issue of the New England Journal of Medicine.

To increase the odds of a successful pregnancy in a woman undergoing IVF, doctors routinely place several embryos in the womb at once, a technique that has led to burgeoning rates of twins, triplets, and "higher-order" multiple births, reported Tarun Jain, MD and colleagues at Brigham and Women's Hospital in Boston, MA. Not only are multiple fetuses associated with increased risks for both mother (e.g., hypertension, anemia, delivery complications) and baby (e.g., prematurity, low birth weight, congenital abnormalities), but they also create a substantial economic burden for parents and society.

With a goal of preventing multiple gestations while maintaining pregnancy rates, the American Society for Reproductive Medicine (ASRM) in conjunction with the Society for Assisted Reproductive Technology (SART) issued voluntary guidelines nearly 7 years ago that recommend maximal numbers of embryos for transfer based on a woman's age, embryo quality, and the opportunity for embryo cryopreservation. The 1999 amended guidelines advise the transfer of no more than 2 embryos in women younger than 35 years of age with good-quality embryos and a sufficient quantity for cryopreservation.

The average number of embryos implanted per attempt fell from 4 to 3 between 1995 and 2001, the last year for which federal data was available. In the last 5 of those years, triplets and greater multiple pregnancies declined from 11% to 7% of all IVF pregnancies, while the rate of twins held steady at about 29%. Without assisted reproduction, just 3% of pregnancies result in multiple births. Furthermore, over the 7-year period, the success rate for IVF rose from 20% to 27%, indicating that assisted reproduction techniques are improving.

"A decrease in the number of embryos transferred per cycle is associated with a decrease in the rate of high-order multiple pregnancies but not in the overall pregnancy rate," the authors summed up. "It is clear that national practice patterns are moving steadily in this positive direction.

Based on these findings, Jain et al concluded that "it is reasonable and prudent to continue professional self-regulation rather than enact new legislation," as several nations already have done, including Brazil, Germany, Hungary, Saudi Arabia, Singapore, Sweden, Switzerland, and the United Kingdom. Laws in these countries limit the number of embryos transferred per cycle to 2 to 4 and punish physician violators with stiff fines, loss of their medical license, or even imprisonment.

IVF had its first US success in 1981; today greater than 1 in 3 US pregnancies result from some form of assisted reproductive technology.

COPYRIGHT 2004 Transplant Communications, Inc.
COPYRIGHT 2007 Gale Group