Vitamin A

During the period of early development, the supply of preformed vitamin A (retinol) must be carefully managed to ensure that the developing fetus is exposed to neither too little nor too much of the nutrient because either condition can have teratogenic consequences. Adequate vitamin A is required for normal embryonic development, and an insufficient supply during pregnancy can result in malformations in the offspring as well as increased mortality and morbidity during early childhood from infectious diseases, such as diarrhea, measles, and respiratory infections.

Excess vitamin A intake has also been associated with teratogenicity in animals and may represent a risk in humans, particularly within the first trimester of pregnancy. Characteristic features include severe motor deficit malformations of the heart, thymus, face, jaw, ears, palate, and brain. Although adverse effects from dietary sources are very rare, events have occurred with the ingestion of high-dose supplements. Although epidemiological data suggest there is no danger when consumption is less than 3000 RE per day, a threshold for any teratologic effects remains to be established.

In Western countries, where vitamin A deficiency is rare, women who are or might become pregnant are advised against taking vitamin A supplements (including cod liver oil), except on the advice of a doctor or antenatal clinic, and not to consume liver or liver products. In developing countries, vitamin A supplementation programs have resulted in decreased pregnancy-related mortality and lower rates of childhood morbidity and mortality, with benefits clearly outweighing any potential risks. The initiation of such programs in any population should be carefully examined in each case according to the risk-benefit ratio, with the final decision taking into account the estimated vitamin A status of the woman, the availability of vitamin A-rich foods, and whether supplementation can be supervised.

Pregnancy Nutrition

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