Calculating Whether Your First Trimester Maternal Blood Screening Test Probability of Down Syndrome or Trisomy 21 / Trisomy 18

So you think your worries stop at getting pregnant? No way. The scary part comes after. Now that you have a precious little life in you,  you have to endure more tests. However, now you’re more connected with your body because you have a precious little life inside of you. All I wanted was for my baby to be okay. After all the hell of getting pregnant, alternating diets, etc., this was my first crazy experience. Just like I first found out I had endometriosis, I didn’t expect myself to have a bad result from a blood test right? Afterall, I’m only 30 years old! They say that anyone under 35 shouldn’t have to worry about Down Syndrome, etc. Little did I know what I was in for.

When I first went to get my blood drawn, the hospital was chaotic. I was in Canada and everyone knows Canada is on nationalized healthcare which means waiting and chaos and horrible help. It took me forever just to find an ob who would even take me and this was through a referral from a doctor from the hospital or NO OB would even take me. I sometimes wonder how women in Canada have babies. More on that later…

Anyway, I was in the hospital, it was chaotic. I waited 2 hours before I went in for a 1 minute blood draw. It was a simple blood draw. Then I went and got my NT scan. I will talk about this in another post. The combination of your blood results and NT scan will let you know your probability of your child having Down Syndrome. Here’s my report:

  • Maternal Age at Term: 31.3 Years
  • Gestation: Singleton
  • Screening Status: Initial sample
  • Gestational Age: 12 weeks 3 days, CRL of 60.0 mm on 11/11/02 (meaning November 2, 2011 for Canadians)
  • PAPP-A: 3.85 IU/L   1.59 MoM
  • free B-hCG: 46.2 IU/L     1.17 MoM
  • NT: 3.2 mm    2.6 MoM 1.72 Delta
  • Down Syndrome: The risk is equal to 1:228 or equivalent to that of a 37.7 year old. The down syndrome risk cut off is 1:350. The risk based on maternal age along is 1:821. The measurement of NT and level of PAPP-A and free B-hCG indicates increased risk of Down Syndrome.

Ok, I freaked out. What do you mean 1:228??? My husband was discussion that if it came out to be 1:10,000 risk, we won’t do any more procedures. Now it’s 1:228? My child has down?????

For you ladies out there, I found a calculator.

Use this calculator and enter in your statistics. It will show you your risk. Variate the NT thickness and you’ll see that if your NT is under 2.0, then your probability goes down dramatically. What affects your NT scan? The person doing your ultrasound. If the person doing your ultrasound is having a bad day (which mine was) then you could have a probability of a down baby just because they have an error!

So anyway, my blood seemed normal if the NT was wrong. I redid the NT scan and it was still over 2.0. It was at 2.4. Therefore, I immediately opted to do a CVS test: Chorionic Villus Sampling. I will continue with this on another post.

Please don’t freak out with your blood report. I freaked out because no one really explained it to me but it’s just giving you a probability and the error measurement is really large! When I redid the blood and NT scan, my odds actually came out worse. My odds became 1:100. Looking back, if I had another baby, I’m going straight to CVS.

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1 Response to Calculating Whether Your First Trimester Maternal Blood Screening Test Probability of Down Syndrome or Trisomy 21 / Trisomy 18

  1. Pingback: Nuchal Translucency Screening – NT Scan for First Trimester Pregnancy Screening | HogHugs

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