Medical tests during pregnancy

Booking Blood tests

Booking blood and urine tests may be done by your GP or we can arrange them for you at your first visit. Sometimes it’s easier for us to organise all the blood tests at once to save you from potentially needing more blood tests later in case we feel we need to check something else.

Full blood count – tests for anaemia.

Diabetes screening

Approximately 10-15% of pregnant women develop gestational diabetes, which can have important implications for their health and the health of their developing baby. Although there are some risk factors for developing diabetes, it is not possible to always predict who may be affected, and for this reason all pregnant women are offered a screening test at approximately 26 to 28 weeks. This test is called the oral glucose challenge test (OCGT) and consists of a blood test taken one hour after consuming 50g of glucose in a provided drink to see how your body has responded to the glucose. If this test suggests you may have diabetes you will need to undergo a further confirmation test called an oral glucose tolerance test (OGCT).

Ultrasound scans

We have an ultrasound machine in our rooms and can check your baby during your clinic visits. You will also have a number of ‘formal’ ultrasounds done during your pregnancy.

Dating ultrasound – this scan is to check the baby’s heart beat, confirm that your due date is correct and to see if you have a multiple pregnancy.

Nuchal scan – this ultrasound is part of the test to assess the risk of the fetus being affected with Down syndrome. It needs to be done between 11 weeks and 13 weeks 6 days. As well as having a general look at the baby, a measurement is taken of the thickness of the layer at the back of the baby’s neck and it is this value that is combined with your blood test results to give an estimate of the baby’s risk of Down syndrome.

Morphology scan – this ultrasound is best done between 18 and 20 weeks of pregnancy. It is a detailed scan done to check the baby’s developing brain, spine, heart, kidneys and other organs. Most babies appear completely normal, but occasionally an abnormality may be found. If this occurs, the finding and the implications for your baby will be fully discussed with you. This scan also checks the growth of the baby, and the location of the placenta in the uterus to ensure it is not too close to the cervix.

Growth scan – this may be done at any stage if we are concerned that the baby is too small or large, or if you have a medical condition such as high blood pressure or diabetes that can affect baby’s growth.

CVS and amniocentensis

Sometimes it is necessary to perform testing on the genetic material of the baby. Common reasons for this include: a high risk of Down syndrome or other chromosomal problems in the fetus based on screening tests or the age of the mother; if there is a known genetic disease in the parents or family such as cystic fibrosis; or if there is an abnormal finding on ultrasound that is suspected to be related to an abnormality in baby’s genetic material. The only way we currently have for accessing baby’s genetic material during pregnancy is by taking a sample of placenta or amniotic fluid from the uterus.

Taking a placental sample is called a CVS (chorionic villus sampling) and taking amniotic fluid is called an amniocentesis (or ‘amnio’). Both of these procedures involve introducing a needle through the woman’s abdominal wall into the uterus and gently removing a tiny sample. Throughout the whole procedure ultrasound is used to guide the position of the needle. It usually only takes a few minutes and although it is uncomfortable, most women find they cope much better than they expect.

The tissue or fluid obtained is sent to a laboratory and the relevant tests performed. Usually the cells from the  sample will need to be grown in culture, which takes time. It can be possible to obtain a preliminary result in a few days, but the final result often takes up to 2 weeks.

CVS is done from 10 to about 14 weeks of pregnancy. The risk of miscarriage in women who have undergone this procedure is estimated at 1 in 100. While CVS has a slightly higher risk of disturbing the pregnancy than
amniocentesis, its advantage is that the result is available earlier in the pregnancy. If a termination is necessary it is a safer procedure in early pregnancy.

Amniocentesis can be done at any time from about 15-16 weeks of pregnancy. The risk of miscarriage is estimated at about 1 in 200.

These tests are done at Adelaide Women’s Imaging – Tennyson Centre or at the Women’s and Children’s Hospital or at Flinders Medical center