These are minimally invasive tests designed to assess the risk of certain genetic disorders or birth defects in each individual pregnancy. These tests may help couples decide if they want to proceed with confirmatory invasive tests:
- Nuchal translucency (NT) assessment performed between 11-14 weeks of pregnancy measures the thickness of a fluid-filled area behind the fetal neck, following strict adherence to standard NT measurement techniques. Down Syndrome babies are usually associated with a thicker than average NT.
- Nasal bone ultrasound scans which reveal an absence of a fetal nasal bone, along with a thickened NT, is associated with a higher risk of having a Down Syndrome baby.
- Maternal serum screening performed between 11-14 weeks or 15-20 weeks may be used alone or in combination with NT and nasal bone assessments to increase the detection rate of Down Syndrome while minimizing invasive testing.
Non-Invasive Prenatal Test (NIPT) are more sensitive and specific at screening for Down, Edwards and Patau syndromes but they cost more. They can even screen for certain sex chromosome abnormalities, triploidy, mircodeletions, DiGeorge syndrome, Angelman syndrome, Cri-du-chat syndrome and Prader-Willi syndrome. The sex of the baby can also be determined. The DNA of the baby can be detected by performing a simple blood test on the mother from 9 weeks into her pregnancy as some of the fetal DNA crosses into the mother’s blood stream. It takes 7-10 days for the results.