What do we check for on the 11 – 13 week Nuchal Down’s syndrome scan?
The Nuchal Down’s syndrome scan is a detailed ultrasound assessment looking at the following:
The size of the baby: to date the pregnancy accurately
Determine and measure the baby’s heart rate.
Measure the nuchal translucency or fluid under the skin at the back of baby’s neck, (NT)read more.
Assess the presence or absence of the baby’s Nasal Bone, (NB) read more.
Assess the blood flow through a vessel close to baby’s heart, the ductus venosus, (DV) read more.
Assess the blood flow through the valve on the right side of baby’s heart for tricuspid regurgitation, (TR) read more.
NEW! Assess the presence or absence of the intracranial translucency, (IT) read more .
Nuchal thickness measurement also demonstrating Nasal Bone
A detailed ultrasound assessment also includes an anatomy survey of the baby. In the first trimester we check the head for its shape and presence of midline brain separation. The baby’s limbs are checked to ascertain that both pairs of limbs are present and the visibility of the stomach, bladder and cord insertion. By doing this we can rule out a vast number of structural abnormalities.
If opting for Nuchal+ screening the risk is calculated using the ultrasound markers and a risk of less than 1 in 300 is classified as low risk
If Addmark® is the screening method the ultrasound assessment is combined with 4 blood markers obtained via a blood sample from the mother to calculate your risk.
Intracranial Translucency Scan
The risk is divided into 3 categories:
If the result is less that 1500 then no further screening is recommended.
If the risk is greater than 1 in 50 it is deemed high enough to consider a diagnostic test, (CVS or amnio)
If the risk is between 50 and 1500 it is recommended that a second blood sample is taken 14 weeks or 2 weeks after the initial blood sample. The second blood sample tracks the profile of the maternal blood markers and a revised risk is calculated. If after this second blood sample the risk is greater than 1 in 250 then again a diagnostic test, (CVS or amnio) should be considered.
It should be pointed out that this is only a guide. Every individual or couple has their own perception of risk and there is not a clear cut off. Everyone has to make their own decision, whether to opt for screening or not and if the risk they are given is acceptable to them.
