Screening Test for Down’s Syndrome
- Down’s syndrome (Trisomy 21) is a condition caused by the presence of an extra chromosome in a baby’s cells. It occurs by chance at conception and is irreversible. Such babies are likely to have other abnormalities especially of the heart. They need to be looked after throughout their life and have a shorter life span (35 – 40 years).
- Screening test are available in your early pregnancy to check if your baby is likely to have Down’s syndrome. It will also assess your risk for Trisomy 18 and Trisomy 13.
- Test is usually done between 11 weeks 0 days and 13 weeks 6 days, the screening test for Down’s syndrome is a combined test of an ultrasound scan and blood test with sensitivity of 70% to 80%.(20% of the results may give false negative) Although the result may show that the baby is in low risk, but some babies may still be found to have down’s syndrome at birth.
- If the result shows that you’re in the high-risk category, you are advised to do a diagnostic test to confirm if your baby has down’s syndrome. This test is usually amniocentesis and this has a small risk of miscarriage (0.5%). Non-invasive Prenatal Test such as Harmony Prenatal Test/Igene Prenatal Test can also be done, however the screening test has a sensitivity of 99% with 1% of false negative result.
- It is advisable for all patients to undergo this test. For couples who wish to continue the pregnancy even if the baby has down’s syndrome are also encouraged to do this test, as the result will give the doctor and paediatrician medical information that will allow them to be prepared on handling the baby at birth and arrange for any necessary treatment that may be required at time of birth.