NEW YORK: The American College of Obstetricians and Gynecologists has recommended that all pregnant women, regardless of their age, should undergo screening for Down's syndrome in the first trimester of their pregnancy.
The recommendation is part of new practice guidelines issued recently. Risk of Down syndrome and other chromosomal abnormalities in offspring can now be predicted easily using highly effective non-invasive screening techniques. The guidelines say those women identified at risk can be offered further screening with invasive tests like amniocentesis or chorionic villus sampling.
Previously, testing for Down Syndrome, a disorder characterized by retardation of the mental growth caused by an extra chromosome, had only been recommended for pregnant women 35 or older, who have been found to be slightly more susceptible to having babies with the defect. Doctors say the risks in older women have been successfully managed and now the highest number of children with Down's syndrome is born to younger women.
Obstetricians have been using assays for three chemicals -- alpha-fetoprotein, unconjugated estriol and human chorionic gonadotropin -- in the mother's blood stream during the first trimester. This so-called triple test identifies about 70 per cent of Down's syndrome cases. It has now been found that accumulation of fluid in the fetus' neck is indication of several chromosomal abnormalities, including Down's syndrome. Hence, obstetricians recommended adding an ultrasound sonography for nuchal translucency to the triple tests to have better detection rates. The new guidelines suggest that all women should be offered a blood and nuchal translucency tests during the first trimester. Those found to be positive in the tests can undergo other invasive tests in the second trimester.
The guidelines are already part of procedures in large academic centers, but private practices, especially in smaller towns and rural areas, do not follow them.
About one in every 800 babies is born with the disorder and the risks rise gradually with maternal age: about one in every 1,200 pregnancies in women aged 25 are affected by it compared to one in every 300 pregnancies for women aged 35.
