Between the 11th and 14th weeks of pregnancy, this test is performed to screen for chromosomal anomalies, primarily Trisomy 21 (Down syndrome). Using ultrasound, the fetal nuchal translucency is measured, and hormone levels from a blood sample taken from the mother are uploaded into a statistical program to determine the fetus's risk of Down syndrome. As a screening test, it does not provide a definitive diagnosis; it only indicates the likelihood of the baby having Down syndrome. A high-risk result does not necessarily mean that the baby has Down syndrome; in such cases, definitive diagnostic tests should be performed. Similarly, even if the test results are not high risk, it cannot be conclusively determined that the baby is free of Down syndrome.
