Pregnant women need lots of vitamin B9 to support their growing babies while staying healthy themselves; however, taking folic acid supplements is not the answer. Not only will the synthetic nutrient fail to help mama and baby, but it could actually end up causing more harm than good. If you have the MTHFR (methylenetetrahydrofolate reductase) gene mutation, for example–and roughly 40% of the population does–your body cannot metabolize folic acid at all. Should this be the case, taking supplements that contain folic acid will result in a buildup of the unmetabolized nutrient. Since it would accumulate on the cell receptors that are looking for actual folate, your body will remain deficient even when you consume foods rich in folate because it thinks it already has enough.