Antenatal Tests for Child Disability
Finding out about child disability in pregnancy
Most babies are born healthy and without disability.
In about 1 in 25 pregnancies (about 4%), a baby has a condition that leads to disability. These conditions and disabilities vary a lot, from mild to very severe, and can affect physical and/or intellectual development.
Antenatal tests can pick up some disabling conditions in pregnancy, including some caused by chromosome and inherited gene abnormalities. It isn’t possible to test for all disabling conditions in pregnancy.
Antenatal tests for child disability: screening and diagnostic
During your pregnancy, your midwife or doctor will recommend that you have some tests to check your health and your baby’s health and development. Some of these tests also check for genetic and other conditions.
If you choose, you can also have other tests in pregnancy to check for conditions caused by chromosome and gene abnormalities, as well as for other conditions such as spina bifida.
The earliest these tests can be done is when you’re about 10-12 weeks pregnant. Different tests are performed at different stages of pregnancy.
Antenatal screening tests can tell you about the risk of your baby having a particular disabling condition, such as Down syndrome – is there an ‘increased’ or ‘low’ risk? Even if you have a ‘low risk’, this doesn’t rule out the possibility of your baby having a condition that causes disability.
After a screening test, you can choose to have follow-up diagnostic tests to get a definite answer.
If you’ve used in-vitro fertilisation (IVF), you can choose to test your embryo at 2-4 days old, before it’s put into the womb. You can’t get this test through the public health system. Your IVF centre can arrange it for you.
If you have a family history of a particular condition, you might choose to have some genetic tests before you’re pregnant. These tests can often be arranged through a genetic counselling service.
Deciding about antenatal tests for child disability
Most parents choose to have antenatal tests for child disability. Many want to know whether their baby has a disability, so they can prepare practically and emotionally before the birth. Others might want to think about the option of ending the pregnancy.
Other parents choose not to have tests in pregnancy. This can be because they wouldn’t choose to end the pregnancy even if there was something wrong, or they want nature to take its course. Others are worried that tests could harm their baby or cause a miscarriage.
You don’t have to have the tests in pregnancy. It’s your choice.
Issues to think about
To help you decide about antenatal tests for child disability, it might be worth thinking and talking with your partner or a support person about some of these issues:
How do you feel about having tests? Anxious? Stressed?
If you get an increased-risk result from a screening test, might you go on to have a diagnostic test?
Would you prefer just to have a diagnostic test, without having screening tests first?
If a diagnostic test shows that your baby does have a condition that causes disability, what might you do?
Do you want information that might make you think about ending your pregnancy?
Are you comfortable knowing that, if you don’t have tests, it’s most likely that your baby won’t have a disability – but that there is a very small chance that your baby will have a disability?
Are you comfortable knowing that not all conditions can be tested for and that the tests are often for specific conditions, not for every disability?
Questions to ask
You might also want to discuss questions and concerns with your GP, obstetrician or midwife. Here are questions you could ask and talk about:
What is my risk of having a baby with Down syndrome or other chromosome abnormalities?
What conditions other than Down syndrome can be diagnosed? What would these conditions mean for my child?
What will the testing cost?
How long will it take to get the results back?
What does ‘low risk’ and ’increased risk’ mean for me and my baby?
How much time do I have to decide about tests?
Where can I get more information about these conditions and tests?
Your decisions about antenatal tests for child disability shouldn’t affect the quality of care you get in pregnancy. Your choices about what to do if you have an increased risk shouldn’t affect quality of care either. You have a right to good and supportive care no matter what decisions you make. If you don’t get it, you have a right to speak to the staff about this or to make a complaint to the health service.
Chromosome abnormalities
For normal human development, we need 46 chromosomes (23 pairs carrying genetic material from each parent) in all of the cells in our bodies.
Chromosome abnormalities are when there are missing or extra chromosomes or changes in the structure or arrangement of the chromosomes. These chromosome abnormalities often cause conditions associated with physical and/or intellectual disability.
Down syndrome is an example of a condition caused by a chromosome abnormality. People with Down syndrome have three copies of chromosome 21 instead of the usual two. This causes intellectual disability and other physical and learning challenges.
Another example is sex chromosome abnormalities. The sex chromosomes are the X and Y chromosomes. Girls normally have two X chromosomes, and boys normally have one Y and one X chromosome. An abnormal number of sex chromosomes might affect development and lead to learning difficulties, although sometimes there are no obvious problems.
Many chromosome abnormalities cause miscarriage or the death of the baby soon after birth.
Gene abnormalities
A baby inherits half of its genes from each parent.
Sometimes one or both parents can pass on gene abnormalities that cause physical and/or intellectual disability. Other times changes happen in a baby’s genes at or during conception.
If you have a family history of a particular genetic condition, or you have another child with the condition, there’s a higher chance that your baby will have the condition.
Cystic fibrosis and thalassaemia are examples of conditions caused by a single gene abnormality.
Other conditions that cause child disability
Other conditions that can be picked up in antenatal tests include physical abnormalities such as spina bifida, and some major heart, stomach or kidney problems. These conditions are often detected using ultrasound and can be diagnosed unexpectedly at a routine ultrasound.