Why don you just do a gene test for Spina Bifida surely that would be more accurate than AFP?
Multiple alleles at multiple loci plus environmental factors are involved in neural tube defects. To develop a NTD an individual would need to inherit a number of risky alleles from both parents. Who are you going to screen? In order to screen fetal DNA you would need to perform an invasive test on the whole population of pregnancies. If you chose to screen the mother you would also need to screen the father. If you identified a number of risky alleles in each , how would you predict whether the fetus had a high risk of inheriting sufficient alleles to cross the threshold? There is no simple prediction of risk as in a single gene disorder such as muscular dystrophy. The current combination of maternal serum AFP screening and ultrasound scanning can detect most cases of NTD cheaply and non-invasively. Current research is trying to make the detection possible at an earlier stage in pregnancy to make it easier for those women who choose to terminate an affected fetus.
