Advances in medical science have provided expectant mothers with a range of genetic tests and screenings to assess the health and wellbeing of the developing foetus. These tests can help identify potential genetic conditions, allowing for informed decision-making and appropriate medical care.
The tests empower expectant parents to make informed decisions and, in some cases, access early interventions. However, it’s crucial to approach these tests with an understanding of their purpose, limitations, and potential emotional impact.
Hospitals don’t always offer all of these tests to every pregnant woman; they decide if the tests are needed based on, for example, the age of the expectant mother or if there has been anything unusual in a scan.
This article explores the various genetic tests and screenings available to pregnant women, their purposes, and the potential implications of the results.
Non-invasive prenatal testing (NIPT): NIPT, typically performed between 10 and 13 weeks, involves a blood test that analyses foetal DNA circulating in the mother’s bloodstream. This test screens for chromosomal abnormalities, such as Down’s syndrome, Edwards’ syndrome, and Patau’s syndrome, with a high level of accuracy. The test comes with a fee in some areas in the UK, so check with your health professional which tests will be offered to you.
Combined first-trimester screening: This screening involves a combination of an ultrasound scan (nuchal translucency) and a blood test (the same as the NIPT), typically between 11 and 14 weeks. It assesses the risk of chromosomal abnormalities and can provide an early indication of potential issues.
Quadruple or triple screen test: Conducted between weeks 15 and 20, this blood test screens for neural tube defects (brain and spine defects) and chromosomal abnormalities by measuring levels of certain substances in the mother’s blood. It assesses alpha-fetoprotein, human chorionic gonadotropin, estriol, and inhibin-A. This test is offered in some hospitals if for any reason a nuchal translucency cannot be performed (e.g. if you are more than 13 weeks at the time of scan).
Anatomy scan (20-22 weeks): While primarily used to assess the baby’s anatomy and development, the anatomy scan may also identify certain structural abnormalities. However, it is not a diagnostic test for genetic conditions.
These tests are usually offered in the case of a high risk screening result or in those who have known genetic diseases.
Chorionic villus sampling (CVS): Offered between weeks 10 and 13, CVS is an invasive diagnostic test that involves taking a small sample of the placenta for genetic analysis. It provides more definitive results for chromosomal abnormalities but carries a slightly higher risk of miscarriage.
Amniocentesis (15-20 weeks): Similar to CVS, amniocentesis is an invasive test performed by extracting a small amount of amniotic fluid for genetic analysis. It is typically offered later in the second trimester and also provides definitive results for chromosomal abnormalities.
Carrier screening: This blood test is conducted on both parents to identify if they carry certain genetic mutations that could be passed on to the baby. It assesses the risk of conditions such as cystic fibrosis and sickle cell anaemia.
Expanded carrier screening: A more comprehensive version of carrier screening, this test assesses a broader range of genetic conditions. It is often recommended for couples with specific ethnic backgrounds that may have a higher risk of certain genetic disorders.
Genetic counselling: This is recommended before undergoing any genetic testing, and you may be referred to a genetic counsellor by your healthcare professional. The counsellor will discuss with you the benefits, limitations, and potential emotional impact of the tests. This is an opportunity for expectant parents to ask questions and make informed decisions about testing. You can choose to say no to any test.
Understanding results: It’s important to approach genetic test results with an understanding of their limitations. A positive result does not guarantee the baby will have a specific condition, and further diagnostic tests may be needed for confirmation.
Making informed decisions: Equipped with the information, expectant parents can make decisions about the pregnancy, considering options such as additional monitoring, medical intervention, or preparing for the potential needs of a child with a condition.
For more information on these tests visit the NHS website.
