Genetic screening, often seen as the best hope for older women undergoing IVF treatment to have a child, is ineffective and actually reduces rates of pregnancies, scientists said on Wednesday.
The surprise finding from a controlled clinical trial involving 408 women is a major setback for a technology that is used increasingly in fertility clinics worldwide.
Couples aiming for a test-tube baby can pay between $3,000 (INR 150,000) and $5,000 (INR 250,000) for a preimplantation genetic screening test. The idea is to study the genetic make-up of embryos before transfer to the womb to make sure they are healthy and likely to survive.
But while the concept is very plausible, Dutch researchers found screening in women aged 35 to 41 years actually made matters worse.
After 12 weeks, only 25 percent of women undergoing in vitro fertilisation (IVF) whose embryos had been screened were pregnant, against 37 percent in the control group. Eventual live birth rates were also lower, at 24 versus 35 percent.
Just why screening cuts the chance of a viable pregnancy is unclear but Sebastiaan Mastenbroek from the Academic Medical Centre of the University of Amsterdam said the test itself might be to blame.
"It is possible that the biopsy of a cell from an early embryo on day three after conception hampers the potential of an embryo to successfully implant, though the effect of biopsy alone on pregnancy rates has not been studied," he said in a statement.
Usually, embryos will have reached the eight-cell stage of development by day three but sometimes there may be as few as four cells, which could in theory make the procedure riskier.
Other factors may be the limited number of chromosomes that can be analysed, which may lead to the transfer of embryos that appear normal but in fact contain faults, and the fact many embryos are "mosaic", where a single cell does not properly reflect the genetic make-up of the whole.
Mastenbroek and colleagues presented their work at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in Lyon, France.
The research was also published online by the New England Journal of Medicine, alongside a recommendation from the team that preimplantation should no longer be performed routinely in older women undergoing IVF therapy.
Fertility experts said the findings were a wake-up call for clinicians and showed the need for more research into the benefits, if any, of preimplantation genetic diagnosis (PGD).
Peter Braude, professor of obstetrics and gynaecology at Kings College London, said the work showed screening did not work in older mothers-to-be and similar studies were needed on whether it helped younger women with repeated IVF failure.
"Vulnerable patients should no longer be exploited financially under the impression that it works," he said.
Joep Geraedts, ESHRE’s chairman elect and a genetics expert at the Dutch-Belgian University Limburg, told Reuters in a telephone interview the new study would come as a shock, particularly in the United States, where PGD is widely used.
"No other medical procedure with such profound medical and ethical consequences has been so poorly studied," Kathy Hudson, director of the Genetics and Public Policy Center at Johns Hopkins University, Baltimore, said.
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