Ideally, women should start taking prenatal vitamins three months before they become pregnant. If you are trying to conceive, start taking prenatal vitamins right away. The mix of vitamins and minerals will not only encourage a healthy pregnancy, but they will create a healthy environment for your growing baby, as well as support early brain development.
If you are not in the category of women who intentionally became pregnant, (like myself) do not stress. Better late than never. Eat a well-balanced diet and supplement with the prenatal vitamin that promotes your diet and lifestyle.