Blood Test Could Expand Range of Conditions Identifiable Before 12 Weeks

07.02.2019

A new blood test has been developed which can identify genetic disorders early in pregnancy by sequencing small amounts of foetal DNA in the mother’s blood.

Non-invasive prenatal tests are already available for chromosomal disorders such as Down 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 effective when one or both parents are known to be carriers for inherited diseases such as sickle cell anaemia, haemophilia or cystic fibrosis.

The new test 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.

Jinglan Zhang at Baylor College of Medicine, Texas, and colleagues tested blood samples from 422 pregnant women, from nine weeks of gestation onwards, from the US, Europe and Asia. Some of them had abnormal results on ultrasound scans suggesting a skeletal disorder in the baby. Thirty-two tested positive for mutations in one of the 30 genes in the test.

For 147 of the participants, the team were able to obtain results from more invasive tests or postnatal tests. Out of these, all of the follow-up tests confirmed that the initial test from the mother’s blood was correct.

New Scientist. January 28. Nature Medicine. January 28.