Tests for your baby during pregnancy
Different types of tests are available during pregnancy to check the health of your baby.
What conditions do these tests screen for or diagnose?
These tests cannot detect all possible conditions, but can often identify:
- chromosomal conditions, such as Down syndrome, Trisomy 13 and Trisomy 18
- some birth defects such as congenital heart conditions and malformed kidneys.
Down syndrome is a condition that results in a range of physical and intellectual disabilities. It is caused by an extra copy of chromosome 21 and is also known as Trisomy 21.
Down syndrome occurs in about 1 in 380 pregnancies. Women of any age can have a baby with Down syndrome, however this risk rises for every year you are older than 35.
Trisomy 18 and Trisomy 13
Both these chromosomal conditions are associated with intellectual and physical disabilities.
A baby born with Trisomy 18 has 3 copies of chromosome 18 instead of the usual 2 copies. The condition occurs in about 1 in 2,000 pregnancies.
Babies with Trisomy 13 have 3 copies of chromosome 13 instead of the usual 2 copies. Trisomy 13 occurs in about 1 in 4,800 pregnancies.
Babies with either Trisomy 13 or Trisomy 18 usually miscarry or, if they are born, rarely live longer than the first month.
Ask your GP for more information on Down syndrome, Trisomy 13 or Trisomy 18.
Neural tube defect
A baby’s brain and spine develop from the neural tube in the first 4 weeks of pregnancy. A neural tube defect occurs when the tube does not fully develop.
Spina bifida occurs when the tube does not completely close along the spine. Other neural tube defects include anencephaly and encephalocele in which the brain and skull do not develop properly.
In Australia, about 1 in every 700 pregnancies is affected by a neural tube defect each year. Taking the vitamin folate before and during pregnancy reduces the risk of your baby having a neural tube defect.
Types of tests
A screening test can show if your baby is at increased risk of a birth defect. Different screening tests are available in the:
The tests do not give a definite diagnosis but will tell you if your baby is at an increased risk of having a chromosomal condition, such as Down syndrome. The results may then help you decide if you want to have a diagnostic test.
A diagnostic test can confirm if your baby has a chromosomal condition or neural tube defect and is very accurate. Diagnostic tests that may be undertaken while you are pregnant include chorionic villus sampling, amniocentesis and ultrasound.
It is up to you whether or not you have screening and diagnostic tests. If you decide to have a screening test and you are later offered a diagnostic test, it is your choice whether or not to have the diagnostic test.
Why have these tests?
Having a prenatal test is a decision for you and your family. It can be helpful to discuss these choices with your doctor or genetic counsellor.
Even if you would not end a pregnancy, knowing whether your baby has special needs can help you to prepare. You may require specialist care during your pregnancy or to book into a specialist hospital for the birth.
You may be unsure whether or not to have prenatal screening. Some questions which you may consider to help you decide include:
- Do I want to know if my baby has Down syndrome, Trisomy 13, Trisomy 18 or a neural tube defect before he or she is born?
- What would I do if my diagnostic test showed my baby has one of these conditions? Would I end the pregnancy? Would I want to know so I could prepare for a child with special needs?
- How will this information affect my feelings and the father of the baby’s feelings throughout the pregnancy?
Talk to your doctor before you decide which, if any, of these tests are appropriate for you.
- Screening tests during pregnancy identify if there is an increased risk of a birth defect.
- Screening tests can often identify increased risk of chromosomal conditions in your baby, such as Down syndrome, Trisomy 13 and Trisomy 18, neural tube defects, such as spina bifida, and some birth defects.
- Screening tests are routinely done in the first trimester (first 3 months of pregnancy) or second trimester (second 3 months of pregnancy).
Office of Population Health Genomics
This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.