First trimester Screening for Down syndr.
Idividualised risk for Down syndrom
The vast majority of the babies are normal . However every woman, despite her age has a small chance of delivering a baby with physical or/and mental dysability.
The only way to know for sure if the baby has a chromozomal or genetic dysorder is by invasive testing as Chorion Villus Sampling (CVS) or Amniocentesis (Amnio). Unfortunately there is 1% chance of Miscarrage due to the procedure.
It is up to you and your partner to decide whether or not the risk of the fetus having a chromosomal abnormality is high enough to warrant having an invasive test. As a guideline, an invasive test is usually offered if the risk of Down’s Syndrome is 1 in 200 or above.
The most accurate way of estimating the risk of the fetus having Down’s Syndrome is carried out at 11-13 weeks and depends on the:
• Age of the mother
• Amount of fluid behind the neck of the fetus (nuchal translucency)
• Presence or absence of the fetal nasal bone
• Fetal heart rate
• Blood flow through the tricuspid valve of the fetal heart
• Blood flow through the ductus venosus in the fetal liver
• Presence or absence of any physical abnormalities
• Level of two hormones (free ß-hCG and PAPP-A) in the mother’s blood
After the scan, on the basis of all the above factors, the estimated risk for Down’s Syndrome will be discussed with you. Only you can then decide if you wish to have an invasive diagnostic test or Panorama test
Irrespective of whether or not you decide to have an invasive test, it is recommended that you have a scan at 20 weeks to check for physical abnormalities.