Embryo Screening may lead to Lower Rates of Pregnancy

A new research in Netherlands has proven that embryo screening tests could be reducing birth rates. Preimplantation genetic screening (PGS), which is supposed to identify emryos that will develop normally, if done by researchers with poor skills, could be responsible for inadvertent killing of the embryos. The study published in the New England Journal of Medicine, suggest that checking of embryos before their usage in in vitro fertilization, where a sperm and an egg are joined outside a woman`s body, could lead to lower rates of pregnancy.

The study was based on 408 women between the age groups of 35 and 41. Half of them were subjected to PGS before in vitro fertilization and half were not. Both the groups had the same rate of miscarriage.

The difference, however between the groups was in the number of women who had viable pregnancies at 12 weeks after treatment. In the control group, it was 37 percent, and in the group whose embryos were screened, it was only 25 percent.

“We found that, at 12 weeks, 25 per cent of the women in the PGS group were pregnant, whereas 37 per cent of the control group had an ongoing pregnancy”, said Sebastiaan Mastenbroek of the University of Amsterdam.

The study showed that PGS did have a link with lower rates of pregnancy, but failed to explain the reason for the link. Mr. Mastenbroek feels that 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. Another reason could be that the PGS is not highlighting the abnormal chromosomes of an embryo which implies that defective embryos are still getting through the screening process.

Mr. Mastenbroek told the European Society of Human Reproduction and Embryology conference in Lyons: “In theory PGS is a great technique, but the practice shows us it’s not.” However, Professor Alan Handyside of the London Bridge Fertility Centre, who pioneered the development of PGS, feels otherwise.

“It is dangerous for people to be saying that PGS has no clinical benefit," he said. "This is simply not our experience and may deprive high-risk patients of treatment they need."

PGS is used in fertility clinics around the globe to screen embryos for chromosomal defects before implantation. Older women, who are at a higher risk of chromosomal abnormalities, make use of PGS before in vitro fertilization. Certain experts are of the opinion that the Dutch group had little experience of PGS and the findings are not conclusive proof of anything.