Pre-Natal Screening Tests

What pre-natal screening tests are available? What are the screening test available to a newly pregnant woman.

The newest test on the market is something called the first trimester screen, or the nuchal-translucency and basically it incorporates 5 different factors. One is maternal age, two is the overall size of the fetus, the crown-rump length of the fetus at that point, and then there are two maternal blood markers that are evaluated, and then the fifth thing is a measurement of a small space on the back of the baby's neck, called the nuchal-translucency, and all five of those things are put into an equation to yield a risk for chromosomal abnormalities. It's generally done between 10 and a half and 13 and a half weeks. The accuracy of the measurement of the nuchal translucency is greatest when it is done in that window. Some of the blood markers can be measured a little bit earlier, but most patients choose to have it all done right around the same time.

Is this an invasive procedure, or a blood test?

Well the screening test and the blood test is not considered invasive. The definition of an invasive procedure is when you actually use some sort of a needle or instrument to go inside the uterus itself, and that would be something like amniocentesis or chorionic villus sampling, CVS. CVS is usually done at 10 – 12 or 10 – 14 weeks, amniocenteses is usually done at 16 – 18 weeks. So many women who find out that they have a positive screen, or an increased risk for Down's Syndrome at the first trimester screen, they may decide to go on and have a CVS rather than waiting for an amniocentesis at 16 – 18 weeks.