WEDNESDAY, April 14, 2004 (HealthDayNews) -- The average number of embryos transferred during an in vitro fertilization attempt has decreased since the late 1990s, and in turn, so has the rate of pregnancies with three or more babies.
In a new study appearing in the April 15 issue of the New England Journal of Medicine, researchers report the average number of embryos transferred began decreasing sharply in 1997, after the American Society for Reproductive Medicine (ASRM) issued guidelines for embryo transfers. Not surprisingly, the researchers also found the number of triplets and higher pregnancies also steeply declined during that time.
"We found improving trends in terms of the average number of embryos transferred and a significant reduction of triplets and higher-order pregnancies," said study co-author Dr. Tarun Jain, a clinical fellow in reproductive endocrinology and infertility at Brigham and Women's Hospital at Harvard Medical School in Boston. "There's a correlation with the enaction of the guidelines and the improving trends. Right after 1998, the high-order pregnancies with triplets or more dramatically flattened out. Prior to that, they were rising exponentially."
In vitro fertilization, commonly known as IVF, has been available to infertile couples in the United States since 1981. Before attempting IVF, women first undergo hormone treatment so they produce multiple eggs. The eggs are harvested, and then placed in a petri dish, where they are mixed with sperm. If an egg is fertilized and begins dividing, it is considered an embryo. One or more embryos are placed into a woman's uterus, with the hope that the embryo will implant and a normal pregnancy will occur.
Because the procedure is time-consuming, emotionally difficult and expensive -- the cost averages more than $12,000 per attempt -- multiple embryos are usually transferred. But when multiple embryos are transferred, multiple gestation pregnancies can occur, often with triplets or more.
Complication rates for multiple pregnancies are much higher than they are for singleton pregnancies. According to the ASRM, mothers pregnant with multiples are more likely to deliver early, develop preeclampsia, have placental abnormalities, develop gestational diabetes, need a Caesarean or have an underweight baby with disabilities.
These complications, along with the rising rate of multiple pregnancies, are the reason ASRM, in conjunction with the Society for Assisted Reproductive Technology (SART), developed guidelines, originally issued in June 1997.
The guidelines suggested women with an above-average chance of a successful IVF procedure should have no more than three embryos transferred during any attempt. Above average was defined as women under 35 whose eggs hadn't been frozen. The recommendation for women with an average prognosis (between 35 and 40) was no more than four embryos at any one try, and for women with a below-average prognosis (those over 40 or who had several failed prior attempts), no more than five.
For this study, Jain and his colleagues analyzed data from the U.S. Centers for Disease Control and Prevention for 1995 through 2001. Outcome information on assisted reproduction attempts is reported to the CDC by fertility clinics. The researchers also included data on the number of multiple births from the National Center for Health Statistics.
According to the study, the number of embryos transferred started decreasing in 1997, but the largest drop -- 11 percent -- occurred during 1998 and 1999. The number of twin births didn't change significantly during this time, but triplets and higher pregnancies started to decrease around the same time. The sharpest decline -- 21 percent -- occurred between 1998 and 1999.
"A couple seeking treatment for infertility should be encouraged by these findings," says study co-author Dr. Mark Hornstein, director of the division of reproductive endocrinology at Brigham and Women's. "We're doing a better job. The same programs are establishing more pregnancies and less multiples."
Hornstein says the guidelines may have contributed to the decline, but also cites improved technology as a reason.
Dr. Jamie Grifo, director of the division of reproductive endocrinology at New York University Medical Center and past president of the Society for Assisted Reproductive Technology, agrees. "A lot of us started working on this before the guidelines," Grifo said. "This study demonstrates that we're getting better because the technology allows us to select better and fewer embryos." He added this study also demonstrates that government regulations aren't necessary for the assisted reproduction field.
"We're all working on this," said Grifo. "Ideally, IVF should get to the point where we can put one embryo in, but right now, success rates are in proportion to how many embryos are transferred." And, Grifo noted, because of the effort and expense involved, most patients want more than one embryo to be transferred.
More information
To learn more about selecting an assisted reproduction center, go to the American Society for Reproductive Medicine. For more information on infertility and assisted reproduction, visit the National Women's Health Information Center.
