Breastfeeding women or women who intend to become pregnant can benefit from taking prenatal vitamins because these pills contain the correct balance of nutrients needed during these circumstances, according to Healthline. Other women should avoid taking prenatal vitamins because the high amount of some nutrients may create health problems.
Breastfeeding women can take a prenatal vitamin to ensure they have enough folic acid and to boost their calcium levels, which are both essential when producing milk, explains BabyMed. Nursing women can also take a regular multivitamin and supplement with folic acid and calcium.
Prenatal vitamins contain too much folic acid for most women, reports Mayo Clinic. Excess folic acid can mask a vitamin B-12 deficiency; however, women of childbearing age, even if they do not intend to become pregnant, may want to discuss taking a folic acid supplement with their doctor so they have enough folic acid in their system in case of an unplanned pregnancy.
Prenatal vitamins provide enough iron for a pregnant woman, but the dosage exceeds the daily requirements for adult women, states Mayo Clinic. A prenatal vitamin may contain three times the recommended dose of iron for a woman over the age of 50. Excess iron can build in a person's bloodstream and can cause constipation, vomiting, nausea and diarrhea.