Cause of ‘Down Syndrome’ cannot be pinned down to maternal age alone

by Medindia Content Team on  October 13, 2006 at 6:12 PM Women Health News   - G J E 4
Cause of ‘Down Syndrome’ cannot be pinned down to maternal age alone
New study unravels that other factors play a strong role along with maternal age in determining the incidence of Down's Syndrome. Many older women who have been either contemplating a planned pregnancy or have found out that they are pregnant often find themselves reeling under the heavy load of traditionally handed down fears of the possibility of having to go through a pregnancy were the chances of the fetus (unborn developing baby) being malformed or mentally challenged, owing to their advanced age.

Well, though the theory is not just a punch in the air, as its medically proven that older women do stand a greater risk in having to give birth to a child afflicted with 'Down's Syndrome'. However, recent research has also brought to the fore other factors alsowhich play a role.

Markus Neuhäuser and Sven Krackow researchers from the Institute of Medical Informatics, Biometry and Epidemiology at University Hospital Essen, in Germany point out that the chances for a baby to be born with Down's Syndrome would also depend on the number of children that have been already borne by his mother and also on the age difference he shares with his nearest sibling.

Their studies based on actual data which data back to a period( when abortions were certainly not in vogue!)from 1953 to 1972, show that the rates of incidence of Down's Syndrome is often considerably higher in older women going through their first pregnancy than older women who have already borne children. Getting Pregnant for the first time around at a later age can be riskier than late second or third pregnancies . A larger gap between pregnancies too seem too favor Down's Syndrome.

Down Syndrome is the result of the genetic abnormality trisomy 21. Trisomy has been the focus of extensive medical research but the exact mechanism is still not understood. One feature common to most trisomies is an increase in frequency of trisomic pregnancies with increasing maternal age. There is strong evidence for uterine selection against genetically disadvantaged embryos. However, as women approach the menopause and the risk of future infertility increases, this selection, or filtering stringency, is expected to relax.

Neuhäuser and Krackow's paper provides evidence that older mothers, who give birth to children with Down Syndrome, have a relaxed stringency of quality control of embryos (or relaxed filtering stringency), which increases the probability that these women will bring children with developmental defects to full term. They believe that this relaxed filtering stringency is an adaptive maternal response and it might explain why the rate of Down Syndrome accelerates with increasing maternal age. These findings have important implications for the prevention of abnormal fetal development. The authors conclude that "clearly, identification of the relaxation control mechanisms and therapeutic restoration of a stringent screen holds promise not only for Down Syndrome."

Source: Eurekalert

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