There are a range of tests and screenings that you might be offered at different stages through your pregnancy. These are sometimes called antenatal tests, and sometimes called prenatal tests or screenings.
These tests are performed to monitor the health and development of the fetus in utero, and can help detect any problems during it's development. There are some that are routinely offered, and additional tests that some women may choose to utilise.
Genetic Health Queensland advises that some of the conditions detected during prenatal screening can be treated after birth; however, some cannot be reversed, and may have serious consequences for the baby. In these cases, some couples consider termination of the pregnancy. This is a very difficult decision and sometimes has to be made in a short space of time, depending on the gestation of the pregnancy when a serious problem is diagnosed. Please call us to talk to a counsellor about your options, or if you are unhappy with the treatment your doctor or health service has given you.
It is also important to note that no prenatal test can guarantee your baby will be normal, and not all conditions can be detected by prenatal diagnosis; however, the majority of couples will have a healthy child.
Genetic Health Queensland states the following.
The most common tests are:
- nuchal translucency ultrasound at 12–14 weeks combined with a blood test (biochemistry) from the pregnant woman;
- detailed ultrasound at 18–20 weeks;
- chorionic villus sampling (CVS) from 11 weeks;
- amniocentesis from 16 weeks.
Some of these are generally only taken up if:
- You already have a child with a serious disorder;
- You or the man involved in the pregnancy have a serious disorder which may be passed onto the pregnancy;
- You have a relative with a serious disorder, or the relative has an affected child;
- You have a family history of a disorder that only affects boys (women may be “carriers” of the disorder);
- You are in your mid 30’s or older.
More information is available via Genetic Health Queensland's downloadable pdf brochure 'Prenatal screening and testing'.
With an ultrasound, sound waves are passed through the uterus and transformed into a picture on a television screen. An ultrasound can be used to determine such things as:
- The gestation of the pregnancy;
- Multiple pregnancies;
- Location of the embryo or fetus early in pregnancy;
- Possible fetal anomalies.
Ultrasounds are non-invasive and have been shown not to cause harm to the fetus.
Combined nuchal translucency screening
This is commonly performed at around 12-14 weeks gestation and is a combined ultrasound and blood test for pregnant women. These are used to calculate the risk of your fetus having Down syndrome or other chromosomal issues. It also assesses whether you are pregnant with twins. You are not required to have this test done. The Queensland Centre for Mothers and Babies has a good decision-making resource [pdf] to help you assess if you would like to access this test or not.
If you have missed your 12-14 week scan due to later diagnosis of the pregnancy itself, or there was another reason you could not have it done, you can take a blood test between 15-20 weeks gestation to assess the likelihood of your fetus developing Down syndrome or spina bifida. This test might not be possible for all pregnancies, so ask your clinician for more details to see if this test is a good one for you to consider.
18-20 week ultrasound
This is a routine scan to assess fetal development and can help identify some structural abnormalities such as spina bifida or heart defects. Not all structural or chromosomal problems can be detected via ultrasound; your clinician can give you more information on what to expect. This is also the scan where it is easiest for the sonographer to tell you the sex of your fetus, should you wish to know.
Chorionic Villus Sampling (CVS)
Performed between the 11th and 12th week of pregnancy, the CVS test involves removal of cells from the placenta via a needle passed through the abdominal wall or vagina (depending on the location of the pregnancy). The test is performed to diagnose chromosomal problems such as Down syndrome. The risk of miscarriage following the procedure is between 1% and 2%.
Performed between the 15th and 19th week of pregnancy the amnio test involves removal of amniotic fluid from the uterus via a needle passed through the abdomen under ultrasound guidance. The fluid removed contains cells shed by the pregnancy. These cells are then grown in a lab until there are enough to test for chromosomal or DNA abnormalities.
The risk of miscarriage following the procedure is around 1%.
With all prenatal testing it is important to remember that a normal test result cannot exclude every possible problem as not all birth defects can be detected by these tests.
For more information on screening tests see the Genetic Health Queensland website or call them on 07 3636 1686.