BEIJING, July 4 (Xinhuanet) -- Pregnancy and live birth rates were substantially lower among women whose embryos were screened for genetic defects before being implanted in the womb, compared with those whose were not, according to a study presented Wednesday at meeting of the European Society of Human Reproduction and Embryology in Lyon, France.

    The findings, which were questioned by some experts, suggest genetic screening should not be a routine part of fertility treatment for women over 35.

    "Based on our research, I would say skip the pre-genetic screening and stick with regular in-vitro fertilization," said Dr. Sebastiaan Mastenbroek from the Center for Reproductive Medicine at the University of Amsterdam.

    In the study, also published Wednesday in the New England Journal of Medicine, Mastenbroek and colleagues were trying to determine the value of pre-genetic screening, a process that involves taking a single cell from a developing embryo to look for chromosomal defects that could lead to problems such as Down's syndrome.

    Doctors have generally thought selecting the most promising embryos will give older women a better chance of getting pregnant. But some experts have expressed concern that fertility centers promote the genetic tests because they are profitable ¡ª with a single test costing as much as 5,000 U.S. dollars.

    The study involved 408 women, aged 35-41 and undergoing three cycles of in-vitro fertilization. The Dutch researchers tested embryos from half of those women.

    Roughly half were assigned to have their embryos screened. Those who received the screening had a substantially lower pregnancy rate than those who did not: 25 percent versus 37 percent. More than 60 percent of the embryos implanted into women who had them screened were abnormal, a clear indication of the difficulties older women face getting pregnant. And in this study, having their embryos screened did not help.

    (Agencies)