DNA method for prenatal diagnosis both effective and safe – forskning.se

The study has been published in the prestigious New England Journal of Medicine
and was conducted on 19,000 women. The study shows that the method
works well also for women with average or low probability to bear children with chromosomal abnormalities, and is also safer than previous methods for prenatal diagnosis.

Amniocentesis has been used for over 40 years to check fetal chromosomal composition. The sample, which has traditionally been through a needle inserted into the stomach of the pregnant woman, seeks to discover whether the child has Down syndrome (trisomy 21) or more severe and unusual chromosomal changes as Edwards syndrome (trisomy 18) and Patau syndrome (trisomy 13 ).

The problem is that each amniocentesis or chorionic villus sampling involves about half a per cent risk of miscarriage.

Right now several evaluations about which method to be offered to Swedish pregnant women: the so-called non-invasive prenatal diagnosis, Nipt, which analyzes fetal DNA from blood samples from the mother, or the so-called KUB test that combines blood tests with ultrasound or a combination of both.

The present study, carried out on 19 000 women, of whom 1500 Swedish, shows that Nipt method has several advantages.

– Since KUB test was introduced, the need for amniocentesis decreased, which is good. But five percent of the women taking KUB test still need to make amniocentesis or chorionic villus sampling, says Bo Jacobsson, professor at the Sahlgrenska Academy and one of the leaders of the study:

– Our results show that Nipt method is both safer and more accurate than the other methods to identify fetuses with trisomies. Right in the current study were identified 100 percent of babies with Down syndrome, which is higher than in the various published compilations, and the risk that the woman still need to take an additional amniocentesis or chorionic villus sampling is less than 0.1 percent.

The new study shows that Nipt method works well not only for pregnant women with high probability of bearing a child with trisomy, but also for pregnant women where the probability is average or low.

– It should be noted that Nipt method is not a diagnostic test, but must be followed by amniocentesis or chorionic villus sampling if the test is positive. Although the accuracy is high, there are a number of false positives that must be ruled with an amniocentesis, says Bo Jacobsson.

Facts
article Cell Free DNA Analyses for Noninvasive Examination of Trisomy published in The New England Journal of Medicine on 2 April.

Link to journal: http://www.nejm.org/