Vitamin A is a crucial micronutrient for pregnant women and their fetuses. It is essential for morphological and functional development and for ocular integrity. In addition, it exerts systemic effects on various fetal organs and fetal skeleton. However, excessive intake of vitamin A during pregnancy may be a concern because, when in excess, it may exert teratogenic effects in the first 60 days after conception.
Vitamin A in pregnancy
According to current evidence, adequate levels of vitamin A during pregnancy are of critical importance to the health of the pregnant woman and her fetus. Unfortunately, to date, vitamin A deficiency in pregnancy is considered a public health problem. In the last decade, few studies have evaluated the nutritional status of vitamin A in Brazilian pregnant women and new studies with new approaches and new projects should be carried out to assess the real magnitude of this problem, particularly in developing countries.
Human studies suggest that low or excessive levels of vitamin A in the diet during pregnancy may result in adverse effects on the fetus. Thus, a recent study evaluated 1,180 pregnant women in the first trimester and observed that 48 newborns had congenital malformations. Therefore, it was observed that the concentrations of selenium, zinc, magnesium and vitamins A, E, B12 and folic acid were significantly lower in mothers of newborns with congenital malformations than in mothers of newborns without malformations, thus highlighting a possible association between malformations and nutritional deficiencies.
During prenatal care, the current recommendation is that vitamin A supplementation should be reserved for the prevention of night blindness in populations with severe deficiency of this micronutrient. More research is needed on the dose and duration of vitamin A supplementation during pregnancy. On the other hand, in places where vitamin A deficiency is rare, caution is recommended with regard to excessive dosage, with vitamin A supplementation or even the intake of foods such as liver that are rich in vitamin A being contraindicated.
Concern about the teratogenicity of vitamin A in humans began with a study, which concluded that a total intake of vitamin A in pregnant women of more than 15,000 IU (4,500 μg retinol equivalent) per day in the diet or more than 10,000 IU (3,000 μg RE) in the form of supplements increases the risk of abnormalities in the development of the neural crest (in which 13-cis-retinoic acid has teratogenic effect).
Clinical practice
Pregnancy is a period of specific nutritional needs for the maintenance of the health of the mother and fetus. In this period, there is an increase in demand for vitamin A, especially in the third trimester due to accelerated fetal development at this stage. In contrast, due to the possible teratogenic effects associated with high doses of vitamin A, excessive intake of this vitamin is worrisome. The main effects associated with excessive intake of vitamin A, particularly early in the first trimester of pregnancy, are congenital malformations involving the central and cardiovascular nervous systems and miscarriage.
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Vitamin A
– Bastos Maia S, Rolland Souza AS, Costa Caminha MF, et al. Vitamin A and Pregnancy: A Narrative Review. Nutrients. 2019;11(3):681. Published 2019 Mar 22. Doi:10.3390/nu11030681
