MSAFP stands for "Maternal Serum Alpha-Fetal Protein". It's a screening test for genetic disorders, sometimes given as a part of the "Triple Screen" test.
Thanks to all who had input on the question of doing the MSAFP test. We've also done a little research elsewhere. Here's what we're seeing in terms of reasonably hard evidence:
So, overall, our risk of a baby born with a condition that could be detected by MSAFP screening is something less than 1/500, probably less than 1/1000.
On the screening side, the numbers we're seeing are that somewhere between 65 and 100 out of 1000 women will be flagged by MSAFP testing for further diagnosis, either via ultrasound or amniocentesis. Amnio, of course, has its own risks. Ultrasound may as well, though the evidence seems spottier on that.
On the birth circumstances side, we're having a hospital birth (we're quite happy with our local small hospital and its attitudes; they seem in favor of all the birth alternatives we have in mind). So we'll have emergency surgery readily available and the possibility of helicopter medevac to Spokane in case of serious issues.
On the philosophical side, we would not choose a second-term abortion, except perhaps for an anencephalic child.
So, to sum it up for us: We're visiting the doctor tomorrow (normal checkup). Unless he has some substantially lower numbers on false positives, or has some reason why this is a higher-risk pregnancy than we think, we're not going to have the MSAFP. The chance of a false positive, and the wait for weeks to get amnio results, just isn't worth the worry.
A new study in the British Medical Journal examined birth records in Wessex to check the relative effectiveness of the Triple Screen in detecting Down's Syndrome. The authors looked at records from 31,000+ live births, and broke them into two categories: those in which the Triple Screen was performed as a first check, and those in which ultrasound plus consideration of maternal age were used as a first check (with follow-up by amniocentesis in either case if there were indications of a possible danger). Their conclusion is that the ultrasound and maternal age method is just as good at detecting Down's in their target population. Their key messages: