Tuesday 6 December 2016

Boy or girl? New tests are accurate at just seven weeks

Independent.ie reporters

Published 10/08/2011 | 11:17

A major new study has shown that non-invasive tests used to determine whether a foetus is male or female are surprisingly accurate even when they are done as early as seven weeks into a pregnancy.

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The study which appeared this week in the Journal of the American Medical Association came up with their findings following analysis representing 3,524 male births and 3,017 female births.

The tests which looked for fragments of the baby's DNA in a sample of the mother's blood came out somewhere between 95pc to 99pc in the accuracy stakes, They can be used well before ultrasound (at 11 weeks) and aren't invasive, unlike other procedures such as amniocentesis, which carries a potential risk of miscarriage.

The simple non-invasive procedure sees researchers check for the child's sex by looking for the "Y" chromosome, which only appears in males. If their sample turns up a "Y" chromosome, it's a boy.

If it doesn't turn up a "Y" chromosome, it's a girl. Of course, it is acknowledged that there is always the slight possibility that the test simply doesn't detect any "Y" chromosome in that particular maternal blood sample.

Encouragingly though the tests were accurate when there was sufficient cell-free foetal DNA in the mum's blood -- at seven weeks' gestation or beyond. The most clear-cut results were found after 20 weeks of a pregnancy. But the analysis found that the Blood tests before seven weeks and any tests using urine were not reliable.

The revelation that this new study provides such a high percentage of reliability to this method that it will almost definitely lead to increased usage by families who want to see if their child is a boy or girl as early as possible in a pregnancy.

It could also be used to look for sex-chromosome-based genetic conditions.

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