Multiple births via in vitro fertilization are declining.

2004 MAY 6 - (NewsRx.com & NewsRx.net) -- A worrisome national surge in multiple births linked to test-tube technology is easing, largely because doctors are implanting fewer embryos during each attempt to make a woman pregnant, a study suggests.

Doctors routinely place several embryos in the womb at once to improve the odds of producing a baby - a technique that sometimes works all too well and leads to twins, triplets, or other multiple births.

But technical advances and the advent of professional guidelines appear to have led to more sparing use of embryos, the study's researchers reported in the April 15, 2004, New England Journal of Medicine (NEJM).

The findings are likely to stoke the debate over whether the government should put a cap on the number of embryos that can be used for each attempt. "It's so rapidly evolving that to put it in the hands of legislation is clearly to temper and limit progress," said Robert Rebar, director of the American Society for Reproductive Medicine. "The guidelines are working."

Researchers at Boston's Brigham and Women's Hospital analyzed federal data on in vitro fertilization (IVF) cases in which women had their own eggs fertilized with sperm in the laboratory and then had them implanted. The technique accounts for the vast majority of laboratory-assisted fertility procedures.

The average number of embryos implanted per attempt dropped from four to three between 1995 to 2001, the last year for which federal data are available. In the last five of those years, triplets and greater multiple pregnancies fell from 11% to 7% of all in vitro pregnancies. The rate of twins held steady among IVF pregnancies, and actually rose among all births in the general population.

Many doctors and parents-to-be hope to avoid multiple births, especially triplets or higher. Such babies are often born dangerously premature and underweight. Such pregnancies can also raise the risk of bleeding, high blood pressure, and other complications in mothers. In addition, children from multiple births impose difficult personal and financial burdens on families.