Conception occurs midway through your cycle, or about two weeks before your period, so you may be unaware you're pregnant until a few weeks into your pregnancy. Important developments of the heart, brain and spinal cord occur in the first two to eight weeks of pregnancy. Taking a prenatal vitamin in the first three months before conception or at least before you are pregnant is important to ensure you have the proper nutrients to support a healthy pregnancy, MayoClinic.com indicates.
Folic Acid, Calcium and Iron
Prenatal vitamins provide certain vital nutrients. You need folate, or folic acid, in a greater amount -- more than 400 mcg -- during pregnancy to help prevent neural tube defects, which are defects of the brain and spinal cord that can develop very early in pregnancy. Extra calcium is crucial during pregnancy to help support strong teeth and bones for both you and your baby. Iron is important to support the development of oxygen-carrying red blood cells and to prevent anemia.
Omega-3s and Vitamin D
Omega-3 fatty acids, which support brain development in your baby, are not found in prenatal vitamins. You can get plenty of omega-3 fatty acids by eating fish, or your doctor can prescribe a supplement for you. Vitamin D is also important in the absorption of calcium but may be lacking in most prenatal vitamins. Drink vitamin D-fortified low-fat milk or consume vitamin D-fortified calcium products. Your doctor may also recommend vitamin D supplements if necessary.
Prenatal Vitamin Nutrient Amounts
Your doctor may prescribe prenatal vitamins for you or recommend a certain brand for you to take that contains adequate vital nutrients for you during pregnancy. If you don't have a prescription and go looking for a vitamin product on your own, understand that not all prenatal vitamins are sufficient. According to the Cleveland Clinic, a prenatal vitamin should contain between 800 and 1,000 mcg of folic acid, 200 to 300 mg of calcium and 30 mg of iron.
Talk to Your Doctor
Avoid combining different dietary supplements unless your doctor recommends it, the American Pregnancy Association advises. You don't need to worry about getting nutrients naturally from foods, but taking supplements in addition to a prenatal vitamin can cause a potential overdose that will be unhealthy for you and your baby.
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