If yoy are expecting, you can buy "prenatal" vitamins to take. The prenatal vitamin is for pregnant women. It contains enough basic vitamins for pregnancy. There are many kinds of brands avaliable on the market. You can find them in Walmart, Target, or other drugstores. The doctor normally suggests you to take more folic acid (usually 800g at least). Folic acid is essential for fetuses in their early development. It prevents major birth defects of her baby’s brain and spine. If you take prenatal vitamins everyday plus good exercise and balanced meals, you should be able to maintain a healthy pregnancy. Just follow doctor`s advice and ask questions if needed.
The below link will take you the US CDC website about Folic Acid. The CDC and the U.S. Public Health Service urge every woman who may become pregnant to get 400 micrograms (400 mcg) of synthetic folic acid every day.
http://www.cdc.gov/node.do/id/0900f3ec80010af9