Checking for Down's syndrome in pregnancy

By Niall Hunter-Editor

The prospect of having a baby with Down syndrome cause considerable anxiety among women, particularly those over the age of 35.

There are tests available to check for this type of fetal abnormality, but they are carried out late in the pregnancy and also carry with them the risk of a possible miscarriage.

However, improvements in ultrasound and blood tests now mean that women can have effective for Down syndrome carried out earlier in the pregnancy and without any possible risks of miscarriage being induced by the test.

A major new study headed by an Irish consultant has shown that over 95% of Down syndrome cases can now be detected in early pregnancy.

Results of the study published in the New England Journal of Medicine demonstrate that new ultrasound and blood tests are now widely available that can detect over 95% of cases of Down syndrome as early as 10 to 12 weeks into a pregnancy.

Over 38,000 pregnant women were provided with a range of ultrasound and blood screening tests at 10 to 13 weeks and then at 15 to 18 weeks gestation.

The study found that screening in the first three months of a pregnancy provided a detection rate of Down syndrome of up to 87%, and that other combinations of screening produced a detection rate of 96%.

The leader of the study, which involved the coordination and analysis of results from 15 US centres, was Prof Fergal Malone, Chairman of the Department of Obstetrics and Gynaecology at the Royal College of Surgeons in Ireland and the Rotunda Hospital.

Prof Malone said concern regarding Down syndrome causes considerable anxiety for pregnant women, especially those aged over 35.

He said the testing approach adopted in the study picks up over 95% of cases of the condition, which is a huge step forward and provides reassurance to the vast majority of women in the very early stages of pregnancy.

Traditional tests for Down syndrome, chorionic villus sampling or amniocentesis, both carry a small risk of miscarriage.

Prof Malone says the new research shows that the vast majority of women can avoid these tests by using ultrasound and blood tests instead.

These pose no risk to pregnancy and give reassurance to the patient early on.

He added that women who are interested in the reassurance that these tests provide should be asking their doctors or midwives for early access to combined ultrasound and blood tests.

He stressed that having an ultrasound test on its own is no longer sufficient and it should be combined with blood tests before the 13th week of pregnancy to test for Down syndrome.

Prof Malone stressed that there are technical challenges for health prpfessionals in performing the special ultrasounds involved properly, as measurements that are off by even a fraction of a millimetre can give very inaccurate results.

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