New York Times, July 12, 2014 by Andrew Pollack
Annika Levitt initially resisted the fertility clinic’s suggestion that only one embryo — rather than the usual two or more — be transferred to her uterus because she was too small to risk carrying more than one baby.
“You go through all that and you put only one back in?” she recalled thinking, fearing it would lower her chances of becoming pregnant.
But her embryos had been tested for chromosomal abnormalities, giving a fair degree of confidence that the chosen one was healthy. “Knowing that it was the strongest of the strong was reassuring,” she said. Ms. Levitt, who lives in Morris County, N.J., gave birth to a girl from that embryo and is now pregnant from another single-embryo transfer.
The chromosomal testing is one of the techniques now coming into use to help fertility clinics answer one of their most vexing questions: Which test-tube embryo or embryos will give a woman the best shot at having a baby?
Another new technique uses time-lapse imaging to study the development pattern of the embryo.
Both techniques can potentially provide more information than the approach now used to judge an embryo’s fitness, which is to look at its shape under a microscope.
That could increase the sometimes frustratingly low efficiency of in vitro fertilization. And if clinics can be nearly certain that an embryo is fit, they might feel more comfortable transferring only one embryo rather than two or more, as is common practice. That would reduce the chances of producing twins or triplets, which face greater health risks than single babies.
“What’s really good about this is we get high rates with singletons,” said Dr. Richard T. Scott Jr, clinical and scientific director at Reproductive Medicine Associates of New Jersey, where Ms. Levitt went.
But some experts say the new techniques, which can add thousands of dollars to the cost of in vitro fertilization, are being heavily promoted without data supporting that they truly improve pregnancy rates. For some women, they say, chromosomal testing, an invasive procedure, might even worsen their chances of getting pregnant.
“A significant portion of women may actually be hurting themselves by doing that,” said Dr. Norbert Gleicher, medical director of the Center for Human Reproduction, a fertility center in Manhattan.
The chromosomal testing is called preimplantation genetic screening, or P.G.S. This is different from a related technique called preimplantation genetic diagnosis, which tests embryos for specific mutations with the goal of preventing the birth of a baby with a genetic disease. With the chromosomal screening, the goal is mainly to improve birthrates, not influence the traits of the baby.
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