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Prenatal testing for chromosome defects using only maternal blood

Many women with high-risk pregnancies elect to undergo amniocentesis or chorionic villus sampling, which are invasive procedures that check for chromosomal abnormalities that carry a risk of miscarriage. However, a revolutionary genetic test has now been developed that can help detect these issues even earlier without putting at risk the fetus. Using the mother’s blood, it is now possible to test for abnormalities, which opens up new debates on what decisions parents will make, when technology can cheaply sequence the entire genome of an unborn child and make it available.

Non-invasive prenatal diagnosis (NIPD) has already been implemented in the UK using cell-free fetal DNA testing, which is based on fetal DNA circulating freely in the maternal blood stream. The test commonly detects three common trisomies defects from the 10th week of pregnancy and in some cases even from the 5th week of conception, but there are also NIPDS that can detect serious X-linked genetic disorders.

The human body has 23 distinct chromosome pairs or copies. Trisomy 21,18 or 13 means there are three copies of either chromosome 21, 18 or 13, instead of two and the technique - which so far has a track of a very small false positive rate - can now detect an increased presence of fetal DNA that contains these extra chromosomes and genetic abnormalities (as in the case of Down Syndrome, Edwards Syndrome and Patau Syndrome).

Currently a large number of women who find out that their babies will be born with these syndromes or others, will make the difficult decision to terminate their pregnancy. When these non-invasive tests will be able to detect defects even earlier, as DNA technology continues to improve in leap and bounds and become much much less expensive, there will be serious bioethical questions. Issues that also could be the cause of heated debates include whether it would be right for future parents to use these types of tests just determine the gender of a child (which is already possible), or test for behavioral or genetic mutations that could impact the lives of their children in the future.

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