Recent discoveries in biology have made it possible to detect many illnesses by testing a person’s DNA. It is also possible to get a sample of an unborn baby’s DNA while it is still in the womb. This means that, in theory, we could start screening unborn babies for many genetic conditions.

This might sound great at first. However, the tests that detect genetic diseases can put the unborn baby at risk. For example, about 1 in 200 amniocenteses lead to complications that can cause a miscarriage of the pregnancy. So if the chances of having a certain genetic disorder are 1 in 1000, more pregnancies will suffer a miscarriage in the testing process than will actually have the disease.

Because of these concerns, tests that are available to pregnant women in BC are strictly regulated. Some common conditions screened are Down syndrome, trisomy 18 and open neural tube defects.

Tests include blood tests, ultrasound exams, chorionic villus sampling and amniocentesis.

Blood Tests
There are several blood tests that look at the amount of pregnancy proteins and hormones in a woman’s blood. Unusual levels of these markers can be a sign of Down syndrome, trisomy 18 or neural tube defects in the baby. These tests don’t say for sure whether or not the baby is affected by these conditions, but will give an idea of how is the likelihood. Because these tests are not invasive and are therefore low medical risk, they are offered to all pregnant women in British Columbia.

Ultrasound
Most parents are excited to go to the ultrasound exam because it gives them a first chance to see their baby. But while mom and dad are watching the little one suck her thumb and doing summersaults, the ultrasound technician carefully examines the baby’s anatomy. This can detect abnormal growth or development of the baby, which can be a sign of many different illnesses. Just like blood tests, ultrasound exams are considered safe for mother and baby. Therefore, at least one ultrasound is offered to all pregnant women.

Chorionic Villus Sampling (CVS)
For CVS, bits of the chorionic villi, which are part of the placenta, are removed and tested. The DNA can then be tested for chromosomal disorders (e.g. trisomy 18) or other genetic diseases (e.g. Tay Sachs).  Because the procedure can cause problems to mother and baby, it is not available to all pregnant women. CVS is only done if there is a high risk of having a baby with a chromosome defect or inheriting a severe single gene disorder.

Amniocentesis
During an amniocentesis, a large needle is put into the womb to get a sample of amniotic fluid, the fluid that surrounds the baby. This fluid contains some of the baby’s cells, which can be used to examine the DNA similar to CVS. Amniocentesis has less risk than CVS but it can still cause problems like infection or even loss of the baby and is therefore reserved for pregnancies at risk of genetic or chromosomal disorders.