Antenatal Risk Assessment
Fortunately, there are screening tests available to help determine the chance of the fetus having specific chromosomal abnormalities like Trisomy 21 (Down Syndrome), Trisomy 18 (Edward’s Syndrome) and Trisomy 13 (Patau Syndrome). Knowing this, couples can then better decide whether they wish to undergo more invasive diagnostic tests.
Also known as the OSCAR (One-Stop Clinic for Assessment of Risk for Fetal Anomalies) test, First Trimester Screening (FTS) combines a maternal blood test with a detailed ultrasound examination to assess the risk of chromosomal abnormalities, particularly Down Syndrome.
This screening is typically performed between 11 and 14 weeks of pregnancy and has a detection rate of about 90%.
During the ultrasound, the nuchal translucency (a fluid-filled space behind the baby’s neck) is measured. Babies with Down Syndrome often have a thicker nuchal translucency. The results of this scan, together with the blood test and the mother’s age, are used to calculate the overall risk. An ultrasound assessment of the fetal nasal bone at this stage can further improve accuracy — a thickened nuchal translucency and absent nasal bone are associated with a higher risk of Down Syndrome.
Between 15 and 20 weeks of pregnancy, a maternal serum screening may be performed to further assess the risk of chromosomal abnormalities.
This blood test measures levels of human chorionic gonadotrophin (hCG) and alpha-fetoprotein (AFP), both produced by the fetus and placenta. These results, combined with maternal age, help estimate the chance of the baby having Down Syndrome.
Our pregnancy clinic also offers Non-Invasive Prenatal Testing (NIPT), a modern screening method for detecting genetic conditions such as Down Syndrome. NIPT carries no risk to the mother or baby, as it involves analyzing a simple blood sample from the mother to detect cell-free fetal DNA.
This advanced test provides a highly accurate and safe alternative for early genetic screening.
