Hello,
I’ve got given a 1/450 score for the Down syndrome screening with the nuchal translucency measured at 1.5mm, so my obstetrician advised me to do the NIPT test (Harmony test).
My doctor in France explained to me what they are mainly looking at when screening for Down syndrome. Here’s her explanation (I have used google translate to translate her explanation so I hope it still makes sense):
“What increases your probability of trisomy 21 are your PAAP-A and Bhcg levels. Indeed, if you have at the same time a low PAAP-A (0.44 times below the value with which it is compared) and a markedly high Bhcg (5.34 times higher than its comparison value). This situation actually increases the risk of T21. However, the production of PAAP-A and Bhcg by the placenta is very variable from one pregnancy to another, even in the absence of trisomy; So if we find more babies with a T21 among women who have a low PAAP-A and a high Bhcg, the majority of them have a baby without T21.”
Not sure if in the UK they give you your full result with your paap-a and Bhcg levels? If so, have a look at your result and check if your papa-a level is low and if your Bhcg levels are much higher than your papa result. If this is the case, it increases your chance of getting a baby with down syndrome (I have included a screenshot of my result as an example).
I still want to reassure you, 1/450 is actually 0,22% for your baby to have Down syndrome! Which is a is a very low risk! I know that in France they have started offering the NIPT test to all women who get a result between 1/1000 and 1/50, as a simple precaution.
Also, your nuchal translucency of 2.5mm seems fine to me. Babies with down syndrome usually have a nuchal translucency measuring over 3.5mm. Lastly, they take your age into account when calculating your score (I know that my age of 38 has worsened my score)!
I've received the result of my NIPT test a couple of months ago and it was all clear so I wouldn’t worry too much if I were you!