Can prenatal screening determine if a baby will eventually have amyotropic lateral sclerosis?

Yes, but ...: Right now we know of about 10 genes that cause als, but there are probably more, because genetic testing finds a mutation in less than a third of ALS that runs in families (10% of als) and in even less when it comes out of the blue. Given a familial mutation, you can test before birth, but prenatal testing is especially complex and is best discussed with a clinical geneticist or genetic counselor.