Chromosomal activities are presently detected through amniocentesis or chorionic villus sampling. Both these approaches seem to be persistent and may stimulate a miscarriage. However experts from the Maastricht University Medical Centre are developing a simple, prenatal blood test to highlight chromosomal activities in the developing foetus.
They have been able to use molecular genetic probes to identify DNA belonging to the foetus specifically in blood sample collected from pregnant women. Until now they have identified the Y chromosome highlighting that the foetus is a boy. Therefore it could be at greater risk of getting affected with an X-linked disorder specifically Duchenne’s muscular dystrophy and haemophilia.
Dr Suzanna Frints, a clinical geneticist at Maastricht University Medical Centre shares, “It is inexpensive compared to the costs of invasive prenatal diagnosis, and could easily be implemented at low cost, between 30-150 Euros per kit per person, with a small apparatus in every hospital in the world. Blood samples can be taken during routine antenatal visits”.
Trisomy 21 can now be identified with the same method; in the future they will investigate trisomy 13 and 18. Scientists used Multiplex Ligation-dependent Probe Amplification method to identify foetal DNA present in the blood of women who have been pregnant for at least six to eight weeks. This method is already a part of an existing kit used universally to identify chromosomal abnormalities in invasively obtained amniotic fluid or chorionic villi samples among pregnant women. This kit is assumed to be cheap and fast to deliver findings within 24-62 hours, however until now it has been used on samples taken during invasive procedures. It is not yet clear if it can be used on cell free foetal DNA circulating in blood samples from pregnant women.
Dr Frints reveals, “The MLPA test results obtained in 2009 were compared with the results of amniocentesis, chorionic villus sampling and pregnancy outcome. All but one sample correlated with the non-invasive MLPA test results, detecting foetal Y-chromosome sequences. At the moment, the reliability of the test is about 80% due to false negative results, but we are working to improve the accuracy of the MLPA probe.”
He further quotes, “Although we need to test and refine this MLPA technique further, our results so far are promising. This is innovative translational research and when we succeed in developing the MLPA procedure for use in maternal blood, we will be able to offer a safe, cheap, fast, reliable and accurate non-invasive test, which will be of immediate benefit to pregnant women, young and old, all over the world.”
This study started in 2009 and is expected to continue to 2012 or beyond. Experts are enlisting women who are at greater risk of abnormal pregnancy and experiencing prenatal screening and invasive diagnostic procedures. In order to collect MLPA proof they included 14 women who had a pregnancy termination between 1- and 22 weeks gestation due to trisomy 13, 18, or 21 identified by invasive prenatal diagnosis. Four women had non-invasive prenatal screening at 12-14 weeks gestation, three women who had invasive prenatal diagnosis because of being at least 36 years old and nine non-pregnant control women who had had up to three children were also observed. In order to finish the trial to evaluate consistency of the MLP technique experts require 20, 715, 40 and 30 women in each group respectively. They anticipate this trial will be available in clinics in two to five years time.
These findings will be presented at the 26th annual meeting of the European Society of Human Reproduction and Embryology in Rome.