Ideally, your diet should be balanced enough to contain all the nutrients you need for a healthy pregnancy. But it doesn't always work out that way. If you have a special diet -- if you're a vegetarian, lactose-intolerant or gluten-intolerant, for example -- or if you're dealing with a major case of morning sickness that makes it hard to keep food down, you may not be able to get all the nutrients you need from your diet alone.
Your pregnancy health care provider will let you know if she thinks a prenatal vitamin is a good idea for you, but if you have specific concerns about your diet, you should bring up the subject at your appointment.
The best time to start taking prenatal vitamins is before you even know you're pregnant. Before some pregnancy tests can even detect that you're pregnant, your body is already hard at work helping your baby develop. Neural tube development, which ultimately affects your baby's brain and spine, occurs during the very first month of pregnancy.
"About 50 percent of pregnancies are unplanned, so it's important for every woman of childbearing age to take a multivitamin with folic acid every day, even if she's not thinking about having a baby," says Ashley Hodges, an assistant professor of nursing at the University of Alabama at Birmingham School of Nursing.
You should keep taking prenatal vitamins throughout your pregnancy, since your baby's nutritional needs will just keep growing. If you plan to breastfeed, you may also want to continue taking prenatal vitamins after you give birth.
Folic acid is the most essential ingredient in your prenatal vitamin, and if your diet is otherwise pretty balanced, it may be the only prenatal supplement you need. Expecting moms and women who are trying to conceive need at least 600 micrograms of folic acid every day, and the Mayo Clinic recommends choosing a prenatal vitamin that contains at least 400-to-800 micrograms of folic acid.
Prenatal vitamins also usually include iron, which your body needs to make red blood cells and protect against anemia. It can be challenging to get enough iron if you don't eat meat or poultry, so it's common for vegans and vegetarians to need prenatal vitamins with this essential mineral. Even omnivores may have a hard time keeping up with the growing need for iron during pregnancy since your circulation system's workload doubles when you're carrying a child. Choose a prenatal vitamin with 30 milligrams of iron, recommends the Mayo Clinic.
Calcium, vitamin C, zinc, copper, vitamin D and vitamin B6 are other common ingredients in prenatal vitamins. Some prenatal vitamins also contain omega-3 fatty acids, which play an important part in healthy brain and vision development for babies. If your prenatal vitamin doesn't contain omega-3 fatty acids -- also known as docosahexaenoic acid, or DHA -- and you don't eat fish, your doctor may recommend you take an omega-3 supplement in addition to your prenatal vitamin.
Prenatal vitamins can make you feel a little queasy, especially if you're prone to morning sickness. If this happens to you, try taking them with a little food -- like crackers -- right before you go to bed at night or first thing in the morning.
If your prenatal vitamins cause constipation, you may need more fiber in your diet. Be sure to drink plenty of fluids throughout the day -- you should be drinking about 10 cups of water every day during pregnancy.
If your vitamin consistently makes you sick, talk to your doctor. She may be able to recommend a different type of vitamin or combination of vitamins that will give you the minerals you need without making you sick.
Prenatal vitamins are designed to fill in potential blanks in an otherwise healthy diet -- they don't replace healthy eating. And too much of a good thing can be really be too much, especially when it comes to certain nutrients, like vitamin A, which can cause birth defects in too-large doses, reports the March of Dimes.