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VITAMINS IN PREGNANCY
Vitamin A
Vitamin A, a fat-soluble vitamin, is important for maintenance of visual function. Its main influence is on the retina, but it also aids glycoprotein synthesis and promotes cellular growth and differentiation in other tissues. Vitamin A is found in green leafy vegetables and yellow-orange vegetables. The nonpregnancy RDA is 800 mcg, and this remains the same in pregnancy. The lactation RDA is 1300 mcg. Well-balanced diets provide the RDA for women who are pregnant or lactating; therefore, routine supplementation is not recommended. Doses exceeding 15,000 IU/d, often used to treat acne, are associated with an increased risk of birth defects and should not be used in pregnancy; however, alpha-carotene, a vitamin A precursor, is not teratogenic.
Vitamin B-1
Vitamin B-1, also known as thiamine, is a water-soluble B-complex vitamin. It is involved in the release of energy from cells. Its food sources include milk and raw grains. The RDA is 1.1 mg. In both pregnancy and lactation, the RDA increases to 1.5 mg. Well-balanced diets provide the pregnant and lactating RDA; therefore, routine supplementation is not recommended.
Vitamin B-2
Vitamin B-2, also known as riboflavin, is a water-soluble B-complex vitamin. It is also involved in the release of energy from cells. Vitamin B-2 is found in green vegetables, milk, eggs, cheese, and fish. The RDA is 1.3 mg. In pregnancy, the RDA increases to 1.6 mg; in lactation, it increases to 1.8 mg. Well-balanced diets provide the RDA for women who are pregnant or lactating; therefore, routine supplementation is not recommended.
Vitamin B-6
Vitamin B-6, also known as pyridoxine, is a water-soluble B-complex vitamin. It is important in protein, carbohydrate, and lipid metabolism. It is also involved in the synthesis of heme compounds. Vitamin B-6 is found mostly in vegetables. The RDA is 1.5 mg. In both pregnancy and lactation, the RDA increases to 2.2 mg. Well-balanced diets provide the pregnant and lactating RDA; therefore, routine supplementation is not recommended.
Vitamin B-12
Vitamin B-12, a water-soluble B-complex vitamin, is essential for DNA synthesis and cell division. It is found in animal proteins. Deficiency is usually secondary to compromised intestinal function. Dietary deficiency is rare, but it is occasionally encountered in persons who follow strict vegan diets. The RDA is 2 mcg. The pregnancy RDA is 2.2 mcg. The RDA increases to 2.6 mcg with lactation. Well-balanced diets provide the RDA for women who are pregnant or lactating; therefore, routine supplementation is not recommended.
Vitamin C
Vitamin C, also known as ascorbic acid, is a water-soluble vitamin with numerous functions. These include reducing free radicals and assisting in procollagen formation. Vitamin C is found in fruits and vegetables. Chronic deficiency impairs collagen synthesis and leads to scurvy. The RDA is 60 mg. The pregnancy RDA is 70 mg. The RDA increases to 95 mg with lactation. Well-balanced diets provide the RDA for women who are pregnant or lactating; therefore, routine supplementation is not recommended.
Vitamin D
Vitamin D, a fat-soluble vitamin, is found in fortified milk. Exposure to ultraviolet light is necessary for vitamin conversion. Deficiency of vitamin D is associated with tooth enamel hypoplasia. The RDA is 200-400 IU. The RDA in both pregnancy and lactation is 400 IU. Well-balanced diets provide the RDA for women who are pregnant or lactating; therefore, routine supplementation is not recommended.
Vitamin E
Vitamin E, a fat-soluble vitamin, is an important antioxidant. It is found in animal protein and fats. Deficiency is not a major issue in obstetrics but has been implicated in newborn hemolytic anemia. The RDA is 8 mg. The pregnancy RDA is 10 mg; the lactation RDA is 12 mg. Well-balanced diets provide the RDA for women who are pregnant or lactating; therefore, routine supplementation is not recommended.
Vitamin K
Vitamin K, a fat-soluble vitamin, is required for synthesis of clotting factors VII, IX, and X. It is found in green leafy vegetables, tomatoes, dairy products, and eggs. Transportation of vitamin K from mother to fetus is limited; nevertheless, significant bleeding problems in the fetus are rare. However, newborn infants are often functionally deficient in vitamin K and receive parenteral supplementation at birth. The RDA is 60 mg. In pregnancy and lactation, the RDA increases modestly to 65 mg. Well-balanced diets provide the RDA for women who are pregnant or lactating RDA; therefore, routine supplementation is not recommended.
Folic Acid
Folic acid, a water-soluble B-complex vitamin, is important for DNA synthesis and cell replication. It is found in fortified grains, dried beans, and leafy greens (American College of Obstetricians and Gynecologists, 1996). Much has been written about folic acid and pregnancy. Deficiency in pregnancy has been linked with maternal megaloblastic anemia and fetal neural tube defects. The RDA is 0.2 mg. The pregnancy RDA is 0.4 mg; the RDA decreases to 0.2 mg in lactation.
In 1998, the US Food and Drug Administration mandated fortification of grains with folate. The degree of fortification was calculated to provide only 0.1 mg/d of dietary folate. This was enacted to avoid having supplemental folate mask evidence of vitamin B-12 deficiency in susceptible populations, especially elderly persons. Cereal fortification has resulted in a 32% decrease in the prevalence of elevated maternal serum alpha-fetoprotein values (Evans, 2004) and a 25% decline in the prevalence of open neural tube defects (Centers for Disease Control and Prevention, 2004).
Despite fortification, sufficient folic acid is not provided by the average American diet and routine supplementation of 0.4 mg/d is recommended for healthy women. Folate supplements should be administered 3 months prior to conception and throughout the first trimester. If the mother has a prior child affected by a neural tube defect, supplementation in the subsequent pregnancy should be increased to 4 mg/d.
Niacin
Niacin is a water-soluble vitamin involved in the release of energy from cells. It is found in poultry, fish, and nuts. Deficiency results in pellagra. The RDA is 15 mcg. In pregnancy, the RDA increases to 17 mcg, and to 20 mcg in lactation. Well-balanced diets provide the RDA for women who are pregnant and lactating; therefore, routine supplementation is not recommended.