Prenatal testing – all you need to know
Will he or she be born with any abnormalities or birth defects, and will you experience any complications?
While most babies are born healthy, concerns such as these are natural. But take comfort in the fact that there are a number of tests available that will allay your fears. These can help identify potential health problems for you and your unborn child, some of which are treatable. It is important to educate yourself and anticipate what you would do should you detect problems. Early detection means more time for treatment and planning various courses of action.
Some prenatal tests are routine in pregnancies and are mostly screening tests. These include blood tests and ultrasounds that can only identify if your baby is likely to have certain conditions but cannot diagnose these with certainty. Diagnostic tests, on the other hand, will either be suggested to you or you may opt to take them. They usually test for chromosomal disorders, which refer to an abnormality in the structure or number of chromosomes.
The chance of a child being born by these disorders increases if the expectant mother is older. For example, the American College of Obstetricians and Gynaecologists found that 1 in 1,667 babies born to women in their early 20s have Down syndrome, but this number increases to 1 in 378 in women in their mid-30s and 1 in 106 for 40-year-old women. Doctors would usually recommend older women or women with a family history of genetic disorders to take these tests. However, an expectant can opt to take them as a precautionary measure as well.
Here are some diagnostic prenatal tests to consider:
Amniocentesis
What: Usually conducted to detect chromosomal abnormalities such as Down syndrome, inherited metabolic disorders and some foetal infections.
Who: The test should be taken if you are above 35 years of age, had a child with a birth defect, have a family history of genetic disorders or had an abnormal screening test.
When: Often performed between 15 and 20 weeks into pregnancy.
How: The doctor will remove some amniotic fluid through the abdominal wall in the uterus during an ultrasound scan with a very thin needle. These cells are grown in a special culture and analysed. You may experience slight pressure or pain, but usually nothing more. Test results are ready within 1-2 weeks.
Risk: Injury to the baby is rare. Risk of miscarriage is 1 in every 200 procedures. There is also a low risk of uterine infection and leakage of amniotic fluid.
Chorionic Villus Sampling(CVS)
What: Usually conducted to detect chromosomal abnormalities such as Down syndrome and inherited disorders. The advantage of this test over amniocentesis is that it can be performed earlier, allowing parents to make decisions and receive counselling.
Who: The test should be taken if you are above 35 years of age, had a child with a birth defect, have a family history of genetic disorders or had an abnormal screening test.
When: Often performed between 10 and 12 weeks into pregnancy.
How: A needle is used to extract tiny placental tissue from your placenta during an ultrasound scan. The tissue is tested for birth defects because the baby originates from the placenta and the specimen would thus have the same chromosomes present in the unborn baby. Mild pain is felt during the procedure and local anaesthesia is used. Test results are ready within 1-2 weeks.
Risk: About 1% of CVS performed result in miscarriage. There are also risks of infection and birth defects developing if the test is done too early in pregnancy.
Foetal Blood Sampling (FBS)
What: Usually conducted to detect chromosomal abnormalities such as Down syndrome, inherited disorders, infections which can affect the foetus and anaemia or low platelet levels in the foetus. The major advantage of this test is that it can be carried out quickly, which is helpful when the foetus is in distress.
Who: The test should be taken after an abnormality is noted on a screening test such as an ultrasound, when other test results are not conclusive or when you have been exposed to an infectious disease that could affect your foetus.
When: Often performed between 18 and 23 weeks of pregnancy.
How: A fine needle is guided from abdomen and into the uterus to extract blood from the foetus during an ultrasound scan. Mild pain may be felt during the procedure and local anaesthesia is used. Test results are ready within three to five days.
Risk: About 1% to 1.5% of FBS performed results in miscarriage.
