Prenatal vitamins are vitamin

Vitamin

A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...

 supplements intended to be taken before and during pregnancy

Pregnancy

Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 and during postnatal

Postnatal

Postnatal is the period beginning immediately after the birth of a child and extending for about six weeks. Another term would be postpartum period, as it refers to the mother...

 lactation

Lactation

Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...

. Although not intended to replace a healthy diet, prenatal vitamins provide women of child bearing age with nutrients recognized by the various health organizations including the American Dietetic Association as helpful for a healthy pregnancy outcome.
Prenatal vitamins are similar to other multivitamins, but do contain different amounts of specific nutrients to better suit the needs of an expecting mother. Vitamins such as folic acid, calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 and iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 are in higher concentrations while nutrients such as Vitamin A are reduced to reflect the current understanding of the role that these compounds play in fetal development.

The increased dosage of folic acid

Folic acid

Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...

 or folates reflects the American Dietetic Associations position that women should consume “400 μg per day of synthetic folic acid from fortified foods (cereals and other grains), supplements or both, in addition to consuming folate from foods in a varied diet.” Often prenatal vitamins also have a reduced dosage of vitamins that may be detrimental to the fetus when taken in high doses (such as Vitamin A

Vitamin A

Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light and color vision...

).
Prenatal vitamins are available both over the counter in retail stores as well as by prescription from medical professionals. Although prescription vitamins are often covered by insurance, the relative potency of prescription-grade products are typically not significantly different than those available through retail. Differences in prescription versus retail vitamins do however exist in consistency and quality level, as well as the relative bioavailability of some specific ingredients. For example, many prescription prenatal vitamins will contain a more bioavailable form of folate; 5-methyltetrahydrofolate (5-MTHF) also known under the brand Merck pharmaceutical brand, Metafolin.http://www.merck-chemicals.com/metafolin-for-stable-health/c_Iiqb.s1LLrYAAAEWY8gfVhTo

Many women have difficulty tolerating prenatal vitamins or experience constipation as a result of the high iron content. Due to tolerance challenges, the prenatal vitamin industry has developed a multitude of dosage forms to meet the needs and tolerances of expecting mothers. The most common form of prenatal vitamin is the compressed tablet which is available through all channels and at various quality levels. Category leaders such as Ther-Rx utilize this as the dosage form of choice. Other organizations within the category offer products in a variety of dosage forms such as liquids, prenatal vitamin soft chews, vitamin chewables, and even jellied prenatal vitamins.

In addition to the actual vitamin, many prenatal manufacturers have chosen to include the omega-3 fatty acid

Omega-3 fatty acid

N−3 fatty acids are essential unsaturated fatty acids with a double bond starting after the third carbon atom from the end of the carbon chain....

, Docosahexaenoic acid

Docosahexaenoic acid

Docosahexaenoic acid is an omega-3 fatty acid that is a primary structural component of the human brain and retina. In chemical structure, DHA is a carboxylic acid with a 22-carbon chain and six cis double bonds; the first double bond is located at the third carbon from the omega end...

 (DHA) in their product, either as an ingredient in the formula, or as a complementary softgel pill. Although explicitly in many formulas to support neural development, the omega-3 fatty acids are used by both mother and fetus to create the phospholipid bilayer that makes up the cell membrane

Cell membrane

The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...

.