Screening Embryos Before Implantation Improves Chances
June 30, 2000 -- Miscarriage is a heartbreaking experience for every woman who experiences it, but when the woman has undergone the ordeal of fertility treatments, including the in vitro fertilization of her eggs, the blow can be crippling.
Even more painful is the experience of a woman who struggles to conceive, but then finds that the baby she is carrying has abnormal chromosomes that can cause a severe defect. Now, a leading researcher says there is a way to avoid either of these sad experiences. The answer, he says, is to examine the embryo for defects before it is implanted in the womb.
The procedure reportedly increases the chances of the tiny embryo planting itself in the wall of the uterus. There also have been reports of a decreased risk of miscarriage and an increased chance of a couple delivering and taking home a live baby.
At least three labs have performed this microscopic genetic checkup on a total of about 1,400 cases, according to Santiago Munne, PhD, director of preimplantation genetics at Saint Barnabas Medical Center in Livingston, N.J. Munne says this testing before an embryo is implanted can help prevent the difficult decisions faced by a woman who is several months pregnant and is then told about an abnormality in her fetus.
The procedure, which involves diagnosing the genetic make-up of the embryo before its implanted, is done on day three of the embryo's development, he tells WebMD. Using molecular probes, "we withdraw one or two cells from the embryo and then analyze the cells for chromosomal abnormalities," he says.
When he examines the cells, he is looking for two common abnormalities. The first defect is called aneuploidy, and it means that the embryo has the wrong number of chromosomes. This is one of the causes of Down syndrome.
Currently, many women, especially those who will be 35 years at the time of delivery, undergo testing during pregnancy to determine if Down syndrome, or other age-related chromosomal abnormalities, are present.
The other defect that he searches for is "translocation of chromosome" -- which is when a whole chromosome, or some part of a chromosome, moves to a wrong position. For about 9% of the women who have repeated miscarriages, translocation is the cause, Munne says.
However, when embryos were checked for chromosomal defects before implantation, the miscarriage rate was only 15%, he says. He says it takes just a few hours to complete the analysis, and the embryo, if it passes this genetic check-up, then can be implanted.
Munne discussed the advantages of screening embryos before implantation at a meeting of the European Society of Human Reproduction and Embryology in Bologna, Italy. He told the gathering of fertility experts "our experience suggests that using [embryo screening] can reduce the risk of delivering a baby with a genetic defect to just 3%."
He says that his center is now offering embryo screening before implantation to all women who undergo in vitro fertilization procedures, but he says that he would not recommend that the technology be used universally.
"I think the only women who should definitely have [their embryos screened before implantation] are those who are 38 or older, or younger women who have a history of miscarriages," Munne says. "The technology is not widely available," he says, adding that he is collaborating with several other centers in the U.S. and Europe, and that he expects other centers to begin offering similar preimplantation genetic screenings.
For more information from WebMD, visit our Diseases and Conditions Pregnancy page.