Delayed motherhood increases the risk of Down syndrome - study

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Down syndrome is a genetic disorder that causes mental retardation and abnormal physical growth. It occurs when an individual has a full or partial extra copy of chromosome 21 (trisomy 21). Down syndrome increases the risk for medical conditions, such as congenital heart defects, respiratory, hearing problems, childhood leukaemia and thyroid conditions. It affects about 1 in 800 babies worldwide and in India, every year more than 23,000 babies are born with Down syndrome.

Prenatal screening essential in at-risk mothers

Prenatal screening is necessary to reveal disorder or conditions that affect the foetus and help improve outcome of pregnancy. There are two types of prenatal screening that are available; non-invasive methods such as ultrasonography and biochemical tests, such as dual marker test in the first trimester (8 to 13.6 weeks gestation age), triple marker test in the second trimester (14 to 22.6 weeks) and quadruple marker test in the third trimester (14 to 22.6 weeks gestation age). The other types of screening are invasive procedures such as amniocentesis and chorionic villous sampling.

In prenatal biochemical markers screening of over 38,081 samples, 6.13% of the total samples were at the risk of Down syndrome. That is over 2334 samples were found positive for Downs Syndrome Risk. The increasing trend of late marriages and delayed first pregnancy that usually occurs between the age group of 31-35 years increases the risk of having a baby born with the syndrome.

The study reveals a worrying trend in the age group of 31-35 years. Out of 9965 samples studied, 7.78% denotes the risk of Down's syndrome pregnancies. Highest number of screened positive cases for Down's syndrome was found in the age group of 35-40 years; out of 2996 samples studied, 21.89% of the results were screened positive. The ACOG (American College of Obstetrician and Gynaecologist) guideline 2007 recommends that every woman regardless of age needs to be screened for Downs Syndrome.

Further testing

All the screened positive (high risk) cases by the statistical calculation needs to be confirmed by invasive procedures such as amniocentesis in second trimester and chorionic villous sampling in first trimester.

Adding on the study Dr Deepak Sanghavi, HOD Clinical Chemistry and Accession, Metropolis Healthcare, Mumbai said, "Down's syndrome is a genetic condition where the child has an extra copy of the 21st chromosome. With the increase in the maternal age, the likelihood of having a child affected with Down's syndrome increases considerably. A woman who is 40 years old at the time of conceiving a child is at a 16 times greater risk of giving birth to a baby affected with Down's syndrome, as compared to a woman who conceives at the age of 25."