Mumbai Nov 03, 2014:
Down syndrome is a genetic disorder that causes mental retardation and abnormal physical growth. Down syndrome occurs when an individual has a full or partial extra copy of chromosome 21 (trisomy 21). Down syndrome increases risk for certain medical conditions such as congenital heart defects, respiratory, hearing problems, childhood leukemia, 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.

October is observed as Down syndrome Awareness Month globally. In order to understand the intensity of the chromosomal disorder in India, Metropolis Healthcare Ltd, the Pathology Specialist, conducted a comprehensive study on 38,081 prenatal screening samples processed in 2014.

Prenatal screening is necessary to reveal disorder or conditions that affect the fetus and help improve outcome of pregnancy. There are two types of prenatal screening that are available; Noninvasive Methods like Ultrasonography and Biochemical test like 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 type of screening is Invasive procedures like 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.

Trisomy 21 Screening by Biochemical markers Test ( 1 year data)

Age group (years)

Test Type

Biochemical trisomy 21 statistical risk

20

21-25

26-30

31-35

35-40

40

Total pregnant Women

Dual Marker

Screen NEGATIVE (low risk)

378

2917

5726

3310

791

43

13165

Screen POSITIVE (High risk )

12

132

312

397

263

52

1168

DM Result

390

3049

6038

3707

1054

95

14333

Triple Marker

Screen NEGATIVE (low risk)

518

3708

6645

4078

1026

36

16011

Screen POSITIVE (High risk )

4

42

159

252

298

83

838

TM Result

522

3750

6804

4330

1324

119

16849

Quadruple marker

Screen NEGATIVE (low risk)

129

1248

2825

1821

523

25

6571

Screen POSITIVE (High risk)

3

26

77

107

95

20

328

QM Result

132

1274

2902

1928

618

45

6899

Total Result

1044

8073

15744

9965

2996

259

38081

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 Gynecologist) guideline 2007 recommends that every woman regardless of Age needs to be screened for Downs Syndrome.

All the screened positive (High risk) cases by the statistical calculation needs to be confirmed by Invasive procedures like 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 Ltd, 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.” CCI Newswire

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