Here’s the second part of doing the first trimester screening. You have to combine this scan with your blood result. We wrote about our blood result in a previous post for First Trimester Blood Screening. This is all to see the risk of whether you child has Downs Syndrome or Trisomy abnormality.
This scan is not scary. It’s just a normal ultrasound. I do have to remind you that whoever does this scan is “SUPER” important and you must make sure they don’t act in haste and that they are very good at what they do because any “little” measurement error changes your odds (therefore I don’t like doing this scan and just opt straight for CVS but that’s just me). My experience on 3 different days all 3 consecutive days the different ultrasound specialists gave me 3 different results: 3.2mm, 2.8mm, 2.4mm. From 3.2mm to 2.4??? That’s a huge difference in the odds if you used the calculator I posted on the previous posts. It was ridiculous.
Anyhow, I just wanted to make sure you’re not totally oblivious when you go in for this scan so this is what the scan should look like and the exact positions they should get your baby to take the measurement. If you don’t have these profiles, your ultrasound specialist is not doing a good job and your results could be flawed. I quickly grabbed these off of http://www.fetalmedicine.com. They have some more in depth things you can look at (http://www.fetalmedicine.com/fmf/training-certification/certificates-of-competence/11-13-week-scan/nuchal/) but to make things simple:
Here’s a good profile of your baby you should see all the things the arrows point out:
The most important is the bottom where it says Nuchal translucency and the next part is you want to see the nasal tip and nasal bone!
The measurement they take is between the two yellow arrows. This for normal babies is usually under 2.0mm to decrease risk of down syndrome. The lower the better of course! The above scan is for a “normal” baby.
This one shows an increased NT probably WAY above 2.0mm. Even if the NT is thick, it doesn’t mean that your baby has down syndrome though. Notice on this scan that the baby still does have a nasal bone. The existence of the nasal bone makes it less of a probability that your baby has downs syndrome! So not to worry, your odds may not be as bad as they seem.
Many doctors don’t tell you that the visual of the nasal bone decreased your odds of your baby having downs by already 1/3 of your usual odds. Without knowing this, you may be relying on erroneous numbers.
What you have to ask yourself now is this. So your odds come back 1:10,000. Are you going to do CVS to be 99% sure? What if your odds came back 1:1000? 1:500? 1:100? Remember that 1:100 just means that 99% chance your baby is normal so at what odd are you going to opt for a CVS or amnio (amniocentesis)?
The NT scan is done right in between 11-14 weeks. I would probably do it right at 11 weeks and some odd days because the bigger they grow, the more inaccurate the scan is as all fluid in the back of the neck goes away as the baby grows.
I’m the kind of person who wants to be “sure” so I opted for CVS right away. I didn’t want to fear throughout my entire pregnancy about my baby being abnormal. Luckily my CVS results came back normal and we’ll be expecting a girl! I’ll post more on CVS and amnio on a different article.
Feel free to comment and share your experience!