NHS Ä¢¹½tvÊÓƵ Prenatal High Chance Screening
We understand that this is a worrying time for you and your family, and you may feel overwhelmed by the complex information you’re receiving as part of your care. You’ve been offered a prenatal invasive test because your screening results suggest a higher chance that your baby may have one of the more common chromosome conditions. We will explain the test in more detail, and additional information is available in patient leaflets and through discussions with your healthcare team. Please feel free to take notes and ask any questions.
To understand why these genetic tests can be helpful, it’s useful to first learn a little more about your baby’s genes. Genes are instructions that tell our bodies how to grow and develop. They are made of DNA and are stored in chromosomes. Normally, we have 46 chromosomes, arranged in 23 pairs. The first 22 pairs are numbered, and the 23rd pair are the sex chromosomes.
Sometimes, during the process of cell division, an extra copy of a chromosome can be passed on to your baby. The most common conditions caused by extra chromosomes are:
. Down syndrome (extra chromosome 21)
. Edwards syndrome (extra chromosome 18)
. Patau syndrome (extra chromosome 13)
A prenatal invasive test can confirm whether your baby has one of these conditions. Deciding whether to have the test is a personal choice, and you may wish to consider what the results could mean for your pregnancy and family.
If you decide to proceed, you’ll be referred to a fetal medicine unit. Your fetal medicine doctor will advise you on the most appropriate test based on ultrasound findings and the ease of obtaining the sample. The tests available may depend on your stage of pregnancy and personal preferences. Both tests provide the same information but carry a small risk of miscarriage, with the national risk being about 1 in 200. This risk may be higher depending on your specific situation.
In some cases, it may not be possible to obtain a result, in which case you may be offered a repeat test.
Preparing for the Test
. On the day of the test, eat and drink as normal.
. Wear comfortable clothing and bring a support person if you wish.
. If you take blood-thinning medications, please discuss this with your healthcare provider before the test.
. After the test, take it easy for 24 hours. Consider any work or childcare arrangements.
The Tests
There are two types of invasive tests:
1. Chorionic Villus Sampling (CVS): A needle is used to take a small piece of tissue from the placenta. This can be done from 11 weeks of pregnancy. In about 1 in 10 cases, the placenta is not in a position that allows the test to be performed, which may require rescheduling.
2. Amniocentesis: A needle is used to take a sample of the amniotic fluid surrounding the baby. This can be done after 15 weeks of pregnancy.
Both tests are guided by ultrasound. During the procedure, a local anaesthetic is used to numb the skin. You may feel some pressure or mild cramping. The procedure usually takes about 5–10 minutes. Afterward, a small plaster will be applied to the area.
You and your partner may also be asked to provide a blood sample to help interpret the results. If your blood type is Rh-negative, you may be given an injection of anti-D immunoglobulin to prevent any immune reactions if your baby has a different blood type.
After the Test
You can go home shortly after the test. Some mild cramping, similar to period pains, is common, and can usually be managed with simple pain relief like paracetamol. It’s fine to shower or bathe after the procedure.
In the rare event of a complication, such as bleeding or infection, these typically occur within two weeks, but can occur up to six weeks later. If you experience vaginal bleeding, watery discharge, severe abdominal pain, or a fever, please contact your local maternity unit for advice.
Results
Your results, known as a qF-PCR, are usually available within two to three working days, though it may take longer in some cases. With your permission, a healthcare professional will contact you with the results. These results will tell you if any chromosomal changes are detected, as well as the sex of your baby.
If a chromosomal condition is detected, your fetal medicine consultant will discuss the findings and explain what they may mean for your baby. This can be an overwhelming experience, and you may want some time to process the information. You may also be referred to UK-based websites and charities for further support.
Some parents may choose to continue their pregnancy, knowing that care will be tailored to meet their and their baby’s needs. Others may decide, after careful consideration, not to continue with the pregnancy, and will be supported in that decision.
The choice to have an invasive test is entirely yours. Your healthcare providers, including your midwife and doctor, are here to support you and answer any questions you may have.
We hope this information helps you and your family make the best decision for your situation.