Okay, it’s premature (ha, see what I did there?) to bid a not-so-fond farewell to the dreaded amniocentesis or CVS for prenatal diagnosis, but a technical report in Nature Medicine shows a great leap forward for pregnant mommies.
Essentially, when you’re pregnant, some of the baby’s DNA makes its way into the bloodstream of the mother and floats around. (It’s called free fetal DNA.) So, if you can draw blood from the mother and figure out which DNA is the baby’s, you can run all those genetic tests without sticking a giant needle into any delicate regions of the mother. And more importantly, you eliminate that small, but very worrisome, risk of miscarriage.
The problem is that there isn’t a lot of that free fetal DNA to work with, so various researchers have come up with different methods to give it a bit of a boost, so to speak, so they can have enough to run tests on.
This particular group says that with their boosting and testing methods, when they tested both normal samples and samples of fetuses with Down’s syndrome (aka trisomy 21), they got it right every time.
If I’m reading the article correctly, the blind portion of the study was only 40 samples, but 100% is still a damn good result. Obviously, this requires more work before it goes into mass production, but it’s a good start.
This is very good news for several reasons. As I said before, anything that lets us eliminate the extra miscarriage risk is a good thing. In addition, the authors think this test would likely be available and useful earlier in pregnancy. (Although it’s not clear to me how early, because I don’t know how long it takes the fetal DNA to circulate widely enough in the mother’s bloodstream to be retrievable.)
For those who are trying to make hard decisions, the earlier you have information about birth defects and genetic problems, the better. Researchers are already looking at how to detect problems other than trisomy 21, so maybe mothers won’t have to face the amniocentesis needle for much longer. And maybe we won’t have to wait until well into the second trimester to learn if babies have Down’s.
Reference: Elisavet A Papageorgiou, Alex Karagrigoriou, Evdokia Tsaliki, Voula Velissariou, Nigel P Carter, & Philippos C Patsalis. Fetal-specific DNA methylation ratio permits noninvasive prenatal diagnosis of trisomy 21. Nature Medicine advance online publication, March 2011.