Blood test can diagnose fetal genetic disorders early in pregnancy
By Sam Wong
A new test allows doctors to diagnose genetic disorders in fetuses early in pregnancy by sequencing small amounts of fetal DNA in the mother’s blood.
Non-invasive prenatal tests are already available for chromosome disorders such as Down’s syndrome. Two years ago, a similar test was developed for recessive single-gene diseases, which occur when someone has two copies of a faulty gene. That test is particularly useful when one or both parents are known to be carriers for inherited diseases such as sickle cell anaemia, haemophilia or cystic fibrosis.
Now there is a test that looks at 30 genes associated with dominant genetic diseases, which occur when someone has just one copy of a faulty gene. These usually occur because of a mutation in the sperm, egg or embryo, and are more common when one of the parents is relatively old. Around one in 600 babies is born with one of these conditions.
The test will likely be used after an ultrasound has shown that the fetus has a skeletal abnormality, or it may be offered to couples in which the father is relatively old.