How accurate is 20 weeks scan?

[GraceBlish]

Hi all, this is my first successful pregnancy after two early miscarriages years ago, and tubal surgery following endometriosis. We were told to go ahead and start the ivf process after trying for nearly 3 years, when I naturally conceived, so this pregnancy means the world to me and my partner.
When we had our dating scan I was already 14 weeks - my gp hadn't made the referral even though I informed him of the pregnancy at 6 weeks! 😡 so we were unable to have the Edwards and Pataus tests. So I was just wondering if anyone knows how likely it is that they would pick any problems up on 20 week scan, or whether it's not guaranteed, I'm just so worried and nervous that there will be a problem after everything we've already been through 😞 TIA

You can get blood tests done if you are concerned. The anomaly scan is more checking organs etc as far as i know. Fingers crossed for you.

honeysucklejasmine is that in the UK? I don't know how I'd go about requesting that! Thank you

Ah, hang on, i am thinking of the blood test for Downs.

According to this link you should be offered alternative scanning to make up for your missed nuchal screening.

www.nhs.uk/conditions/pregnancy-and-baby/pages/screening-amniocentesis-downs-syndrome.aspx

How far along are you now? Have you spoken with your midwife about your concerns and to see if they can offer anything?

I do know that you can pay for a private blood test that screens for genetic/chromosomal conditions. I think they are a few hundred pounds though but something you could consider if it is within your reach to do so.

We had the downs blood test and the "other tests" they offer are just the usual mid-term 20 week scan where they check for physical abnormalities (as I guess they would say if Edwards or Pataus then it may display in physical problems). I guess my interest is just whether anyone who didn't have the blood tests for E or P's had anything picked up during their scan at 20 weeks?
Thanks LikeaSnowFlake, Unfortunately we're not in the position to afford a private test :(

Could you request a nipt test at the hospital? They test placental DNA for Downs, Edwards and Pateau's. No limit on the timing. 99% accuracy.

We paid around £270 to have it done privately at the hosp, but they may not charge you if you explain your circs.

I am sure that Edwards or Patau would show up on the 20 week scan, if the pregnancy had even managed to progress that far (a lot of Edwards/Patau pregnancies result in miscarriage).

Unfortunately at my 13 week scan several issues that could indicate Edwards/Patau were already visible (slow growth, exomphalos, raised nuchal translucency, and single umbilical artery) even though the hand and feet abnormalities and cardiac/brain problems aren't obvious at that gestation.

My blood results (extremely low PAPP a and free Beta HCG) were also a red flag.

Anomaly scans are very detailed, the idea that an experienced sonographer wouldn't spot the traits of Edwards or Patau at that point seems very unlikely, but if they did pick on anything untoward you could always have an amnio.

Thanks GreedyDuck, and I'm sorry to hear things didn't go well for you during your pregnancy ❤ all the best for the future ❤

The detection rate of Edwards and pataus at the 20/40 anomaly scan is 99% it would be very unlikely to go undetected x

JackiePiper - excellent thank you! That has put my mind at rest, really appreciate that ❤

Most T18 and T13 pregnancies are detected at the 20 week scan (my daughter's t18 signs were spotted then) however I know at least 50 families with postnatal diagnoses so if you would terminate I'd opt for NIPT to be sure

PirateQueen, Edwards and Pataus syndrome babies are the most serious of the three as they are generally not compatible with life. Luckily often these anomalies are picked up at the anomaly scan. Only 50% of babies with Downs will be picked up at scan but it is a less serious condition, with most being picked up due to a heart anomaly. Ask to speak to the screening co-ordinator midwife if you have more questions, they are often really helpful. Good luck!