All women of childbearing age are encouraged to increase their intake of folate. That's been the case ever since it was discovered that women who had diets low in folate were more likely to have babies with birth defects, including spina bifida, in which a baby's spinal cord doesn't develop properly.
So prenatal vitamins, which have higher levels of folic acid than regular vitamins, are prescribed for women who are pregnant, and they're also recommended for women who are planning on trying to conceive, since birth defects can occur very early in a pregnancy, before a woman even knows she's pregnant. Today, many of the nation’s breads and cereals are now fortified with folic acid as well. And often pregnant women will conscientiously increase their intake of fruits and vegetables, which naturally contain folate, along with taking their prenatal vitamin daily.