Spinal bifia -- is there anything that would prevent it?

Folic acid: Taking Folic Acid or folate supplements has been shown to decrease the risk of spina bifida. But a pregnant woman must start taking it early in pregnancy. So if you are trying to get pregnant you should already be taking it or a multivitamin with 400 micrograms (0.4 mg) of folic acid. If you're already pregnant, take the same dosage if you're not on a pregnancy vitamin already.

Folic acid: Genetic predisposition causes spina bifida, especially combined with environmental factors. Deficiency of Folic Acid is a major contributing factor to developing this, which is why prenatal vitamins are heavily fortified with folic acid. This will not prevent all cases.