One relatively new way to avoid amnio and CVS is called a genetic sonogram, which is "a sophisticated ultrasound that details the fetal anatomy ... looking for the presence of major fetal anomalies or specific anatomic features (so-called 'soft markers') that might be found in a child with Down syndrome."
In a recent study of 8000 pregnant women screened for fetal chromosomal abnormalities,
The detection rate of Down syndrome babies varied from 69 percent for the genetic sonogram alone to as high as 98 percent with certain combinations of the biochemical markers. More importantly, the improved detection rate was accompanied by a decrease in the screening tests false positive rates.
So using the current method of choosing whom to give amniocentesis to, and then giving them a sonogram instead of amnio, gives 2% false negatives and a smaller number of false positives than from just the blood tests. Since amnio gives no false positives or false negatives, a woman will have to weigh the current risk of amnio or CVS against the new error rates.
- If you would want to abort a fetus if it turns out to have Down syndrome, how much risk is a 2% chance of having such a kid anyway?
- How bad would you feel about the chance of aborting a kid that in fact did not have Down syndrome?