How Accurate Are Prenatal Screening Test?

[next.med88]

Unfortunately, somebody I really care about just got a prenatal screening test result back and it was found out that it was at high risk for trisomy 18.

 

How accurate are these? I know this is a screening test, so it is not accurate and definitive like a diagnostic test, but how often is it wrong?

 

I know this isn't the ideal place to ask this question, but unfortunately since this isn't about myself I can't just go ask my doctor, and googling all of this information on prenatal screen is driving me insane!

[Lactic Folly]

http://sogc.org/publications/prenatal-screening/

 

"The results are not a diagnosis. They tell you a likelihood that your baby has a condition."

 

"A ‘positive’ screen means that your risk is over a certain threshold – there is a chance (usually small) that your baby has one of the conditions you were tested for. More diagnostic testing may be offered to you. These additional tests, such as amniocentesis, can give you a better idea of whether your baby has one of these conditions. You and your health-care provider can use this information to make decisions about your pregnancy and help you prepare for the birth of your child.

However, these additional tests come with risks, such as a 1 in 200 chance of miscarriage. Not all women choose to have additional tests; the choice is yours.

Prenatal screening tells you the chance that your baby might have a condition. It does not tell you for sure. Most women who have a ‘positive’ screen result will not have a child with a condition. Only further diagnostic testing can tell you for sure. For example, a 1 in 100 risk means a 99 in 100 chance of having a baby without the condition."