Non-invasive prenatal diagnosis (NIPD) Prenatal diagnosis and testing

It has been known for some time that DNA from the baby can be detected in the mother’s blood, early in a pregnancy.

NIPD is a new test that has recently been developed, which can extract the baby’s DNA directly from a routine blood test taken from the mother. This test cannot always be used to determine whether the foetus is affected by a musclewasting condition – but it can be used to find out the sex of the foetus.

Knowing the foetal sex may be important for women who are carriers of types of musclewasting conditions that affect mainly males (see our leaflets on Inheritance and the muscular dystrophies).

Women who know they are having a boy may then want to have further tests, such as CVS or amniocentesis (see below). Women who know they are having a girl, do not need to proceed to any further prenatal testing that may put the pregnancy at risk.

Women who are considering NIPD should discuss this with their doctor or genetic counsellor. This would be important to establish whether or not this test would be appropriate and available for them, as well as the accuracy of this testing for their particular condition.

What does the test involve?

NIPD is done on a sample of the mother’s blood, taken from the arm. NIPD to determine the sex of the foetus can be done from seven weeks into the pregnancy.

How accurate is the test?

NIPD tests to determine the sex of the foetus are around 99 percent accurate. Your geneticist will discuss all these factors with you before any test, and will explain whether or not there is likely to be a risk of error with the test result.

What are the risks of the test?

Because NIPD testing is via a blood sample, there is no risk to the pregnancy.