Genetic screening options for women

In pregnancy, we offer the option to screen for some genetic conditions that could affect the pregnancy. While 97 per cent of babies are born healthy, 2-3 per cent of babies are born with some type of abnormality, which can range from something minor (e.g. an extra finger) to something major (e.g. a heart or brain malformation). We can screen for a few conditions that cause abnormalities but not all. Early on in the pregnancy we are able to screen for Down Syndrome, Trisomy 18 and Trisomy 13 (genetic conditions similar to Down Syndrome with an extra chromosome 13 or 18, which are much less common and far more severe). The risk of a baby being born with any of these conditions, including Down Syndrome is related to the mother's age, and increases as the mother gets older.

First trimester screen

At present the most common test is called FTS or first trimester screen and involves blood work, and an ultrasound at approximately 12 weeks. It does not put the baby at risk and it is covered by OHIP. This test detects about 85-90 per cent cases of Down’s Syndrome, Trisomy 18 and Trisomy 13, however, a positive test is possible with a normal baby in 3-5 per cent of cases. Results are provided within 1-2 weeks of testing. In the event of a positive test, most women will be referred on for further testing before a diagnosis can be made.

Non-invasive prenatal testing

There is also a test called NIPT or non-invasive prenatal testing. This test is usually not covered by OHIP (unless the patient is at high risk of chromosome abnormality). It involves blood work done and can be done as early as 10 weeks. It tests for Down Syndrome, Trisomy 18 ,Trisomy 13 and sex chromosome abnormalities with >99 per cent accuracy. With time, further testing has been added but the detection rate is variable. At present it costs $495 and results are provided in 1-2 weeks.

18-20 week ultrasound

In addition to the above, all women are offered an ultrasound at 18-20 weeks to look for major anatomical abnormalities. Ultrasound can detect approximately 80 per cent of major anomalies.