Vitamin A is a general term used to describe two different nutrients you can get from supplements or various foods in your diet. Pregnant women need to get a certain amount of these nutrients in order to ensure the health of their developing fetuses. However, vitamin A overconsumption can lead to a toxic fetal reaction that triggers the onset of birth defects.
Vitamin A Basics
One type of vitamin A, called retinol or preformed vitamin A, can be used by the human body without any further chemical transformations. It comes from animal-based foods, including liver, eggs and milk. The second type of the vitamin, called carotenoids or provitamin A, must be chemically converted inside your body. The main carotenoid in the human diet, called beta-carotene, comes from a wide variety of fruits and vegetables, including spinach, apricots, carrots, peaches, peppers, kale, peas, mangos and papaya. Prenatal vitamin A supplements typically contain beta-carotene, but you can also purchase supplements or fortified foods that contain retinol.
Toxicity
You can develop Vitamin A toxicity through overconsumption of retinol or preformed vitamin A, but not from overconsumption of beta-carotene or other carotenoids, according to the "Merck Manual for Healthcare Professionals." Typically, toxicity leading to birth defects occurs as a result of chronic, or long-term, overuse of retinol. Potential symptoms of chronic toxicity include hair loss in your eyebrows, the development of coarse and sparse head hair, dry eyes, cracked lips, severe headaches, general body weakness, easy bone fracture and development of a brain condition called pseudotumor cerebri. The birth defects associated with vitamin A toxicity are not reversible.
Maximum Safe Intake
The National Academy of Science's Institute of Medicine calculates vitamin A intake in measurements called retinol activity equivalents, or RAEs. One mcg of retinol equals 1 RAE, while 12 mcg of beta-carotene equals 1 RAE; 24 mcg of another carotenoid, called alpha-carotene, also equals 1 RAE. To avoid the possibility of birth defects, pregnant women between the ages of 19 and 50 have a maximum safe daily intake of 3,000 mcg RAE, or 10,000 IU. Pregnant adolescents have a maximum safe daily intake of 2,800 mcg RAE, or 9,320 IU.
Considerations
Despite the potential for vitamin A toxicity, developing fetuses rely on retinol and a retinol breakdown product called retinoic acid for normal development, Oregon State University's Linus Pauling Institute notes. Specific aspects of growth that require retinoic acid include growth hormone regulation, limb development and eye, ear and heart formation. Pregnant women 19 or older need at least 770 mcg RAE of retinol per day, while pregnant adolescents need at least 750 mcg RAE. In addition to food or supplement sources, pregnant women can develop vitamin A toxicity if they use isotretinoin or other medications related to retinol. Consult your doctor for more information on vitamin A, vitamin A toxicity and fetal health.
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