NHS Ä¢¹½tvÊÓƵ Prenatal Unexpected Find
Thank you for listening. We understand that this is a worrying time for you and your family, and you may feel overwhelmed by the new, sometimes complex information you are receiving as part of your care. You may have been offered various tests to help understand the cause of unexpected findings on your antenatal ultrasound scan. One of the tests offered is a prenatal invasive test, which may identify a genetic cause for the findings seen in your baby. We will explain this test in more detail, and additional information is available through relevant patient leaflets and discussions with your healthcare professionals. Please feel free to take notes, and they will be happy to answer any questions you may have.
To understand why these genetic tests can be helpful, it’s useful to first learn a bit about your baby’s genes. Genes are instructions that tell our bodies how to grow and develop. They are made of DNA and stored in our chromosomes. Chromosomes come in pairs, and we usually have 46 in total. These are numbered from 1 to 22, and the 23rd pair are the sex chromosomes.
As we develop, cells divide and multiply to form the baby. Occasionally, through no fault of your own, this process can result in an extra copy of a chromosome in some or all of the baby’s cells. The most common extra copies are of chromosome 21 (known as Down syndrome), chromosome 18 (Edwards syndrome), and chromosome 13 (Patau syndrome). Sometimes, a variation can occur in the sex chromosomes; the most common condition is Turner syndrome. In rare cases, unexpected findings on ultrasound can be due to a more unusual genetic change, where some genetic material is missing, moved, or added to a chromosome.
Choosing to have a test is a personal decision. You may wish to consider what the results could mean for your pregnancy and family. If you decide to proceed, you will be referred to your nearest fetal medicine unit, where a fetal medicine doctor will advise on the best test based on ultrasound findings and the ease of obtaining the sample. Both tests will provide the same results and carry similar risks. Invasive tests are associated with a small additional risk of miscarriage—approximately one in 200, although this may be higher depending on your ultrasound findings. In some cases, it may not be possible to obtain a result, in which case you would be offered a repeat test.
To prepare for the test, you can eat and drink as usual, wear comfortable clothing, and bring a partner or another adult for support. If you take blood-thinning medications, please discuss this with your healthcare provider prior to your appointment. After the test, take it easy for 24 hours and consider any work or childcare arrangements.
Two types of invasive tests are available:
1. Chorionic Villus Sampling (CVS): This test uses a needle to obtain a small piece of tissue from the placenta (the afterbirth). It can be performed as early as 11 weeks of pregnancy. In about 1 in 10 pregnancies, the placenta may not be in a position that allows the test to be performed, in which case the test would need to be delayed.
2. Amniocentesis: This test uses a needle to take a sample of the amniotic fluid that surrounds the baby. It can be performed after 15 weeks of pregnancy and involves an ultrasound scan throughout the procedure. An antiseptic solution will be applied to clean your tummy. If you have a CVS, a local anesthetic will be used to numb the skin, which may briefly feel like a stinging sensation. The needle is guided into the placenta or amniotic fluid, away from the baby. You may feel a pushing sensation or mild tummy cramps. Once the sample is obtained, the needle is removed, and a small plaster is applied to your tummy. The procedure typically takes 5 to 10 minutes.
After the test, you and your partner may be asked to provide a blood sample to help with the analysis. If your blood group is rhesus negative, there is a chance that your baby’s red blood cells could enter your bloodstream, in which case you may be offered an injection of anti-D immunoglobulin to prevent any potential issues with antibodies.
You can go home shortly after the procedure. It is common to experience some mild period-type cramps, which should resolve with simple pain relief like paracetamol. You can bathe or shower as usual.
If a complication were to occur, it would typically be within two weeks of the procedure, though it could occur up to six weeks later. If you experience vaginal bleeding, watery vaginal discharge, worsening abdominal cramps, or a high temperature, please contact your local maternity unit for advice.
You will receive two test results:
1. qf-PCR: This test will screen for common chromosomal conditions, including Down syndrome, Edwards syndrome, Patau syndrome, and some sex chromosome variations. Results are typically available within 2 to 3 working days, but occasionally may take longer. With your consent, you will receive these results directly from one of your healthcare professionals.
2. Microarray: If the qf-PCR doesn’t identify a common chromosomal change, a more detailed test called a microarray will be performed to look for rarer genetic changes. This test typically takes 2 to 3 weeks to complete. Occasionally, a chromosome change may be found that is not yet fully understood, or one that does not explain the ultrasound findings. If this happens, your doctor will discuss the findings with you in detail.
As with all medical data, your genetic test results will be stored securely by the NHS. In some cases, further testing may be recommended, such as prenatal exome sequencing, and your doctor will discuss this with you if appropriate.
It is important to note that genetic testing does not always provide answers, and prenatal tests do not rule out all possible genetic conditions. You may need time to process the information and may wish to access support from UK-based charities and websites specializing in this area.
If a chromosome change is detected, some parents choose to continue the pregnancy with the understanding that care will be tailored to their baby’s individual needs. Others, after careful consideration, may choose not to continue with the pregnancy, knowing that they will be supported in their decision. Ultimately, the decision to proceed with genetic testing is yours. Your maternity care team, including your midwife and doctor, are here to support you and will be happy to answer any questions you have.
We hope this information helps you and your family during this time.