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Vitamin A supplementation during pregnancy is very important for visual function, immunity in particular and fetal growth and development in general. However, pregnant women need to take the recommended dose of vitamin A to avoid adverse reactions to the baby.
1. Importance of vitamin A supplementation during pregnancy
Vitamin A is an important micronutrient for the health of pregnant women and fetuses. Vitamin A not only supports the development of morphological, functional and intact eyes, but also has systemic effects, especially on some specialized organs and fetal bone development. Therefore, vitamin A supplementation during pregnancy is essential.
Vitamin A deficiency in pregnant women is the leading cause of corneal damage in the fetus, the risk of permanent blindness if not treated promptly. Most pregnant women in developing countries experience vitamin A deficiency during pregnancy.
In contrast, in some developed countries, excessive vitamin A supplementation during pregnancy is a major concern. If an overdose of vitamin A is given to pregnant women, this micronutrient can cause birth defects, especially in the first 60 days after conception. In addition, regular prenatal vitamin A supplementation is not recommended.
However, in areas and countries where vitamin A deficiency is a serious public health problem, vitamin A supplementation during pregnancy is recommended to prevent night blindness. Pregnant women are encouraged to get adequate nutrition, preferably through a healthy, balanced diet.
Thiếu vitamin A ở phụ nữ mang thai là nguyên nhân hàng đầu gây tổn thương giác mạc ở thai nhi
2. Sources of vitamin A for pregnant women
In humans, vitamin A has three major active forms (including retinal, retinol, retinoic acid) and a stored form in the liver (retinyl ester). The body cannot synthesize vitamin A on its own, so the main source for the body is through the diet, including 2 main sources: converted vitamin A (in the form of retinol and retinyl ester) and provitamin A. (carotenoids, mainly beta-carotene and alpha-carotene).
Metabolized vitamin A is found in foods of animal origin such as dairy products (including milk, yogurt and cheese), liver, fish oils and breast milk. Provitamin A is found in many plants, such as fruits, vegetables and tubers such as carrots, pumpkin, kale, spinach, sweet potatoes, papayas, and mangoes. Absorption of vitamin A from plant sources is often worse than from animal sources.
The process of absorption and metabolism of vitamin A in the body is related to the ability to absorb lipids. For those on an extremely low-fat diet (less than 5 - 10g/day) or those with frequent pancreatic, liver and gastroenteritis diseases, which interfere with the digestive process. lipid metabolism and absorption, leading to malabsorption of vitamin A.
3. How is vitamin A transported from mother to child?
Transport of vitamin A from mother to child occurs across the placenta during pregnancy, birth, and through the mammary glands during lactation. During pregnancy, maternal serum retinol concentrations decrease (especially during the third trimester) and the placental barrier selectively results in decreased vitamin A stores in the neonate to avoid the risk of malformations. disability caused by an excess of vitamin A.
After birth, the majority of serum retinol is transported to the breast, into breast milk and passed on to the infant. Therefore, the transport of vitamin A through breast milk during the first 6 months of life provides 60 times more vitamin A than through the placenta during the entire pregnancy. Furthermore, breast milk also provides active vitamin A provitamin A (carotenoids), which act as additional essential nutrients for the infant.
Trắc nghiệm: Bạn có hiểu đúng về dấu hiệu mang thai sớm?
Các dấu hiệu mang thai sớm không phải chỉ mỗi trễ kinh mà còn có rất nhiều dấu hiệu khác như xuất huyết âm đạo, ngực căng tức,… Điểm xem bạn biết được bao nhiêu dấu hiệu mang thai sớm thông qua bài trắc nghiệm này nhé!
4. Risk of vitamin A deficiency during pregnancy
Vitamin A deficiency is a global problem, along with iron and iodine deficiency anemia.
Theoretically, everyone is at risk for this condition at any stage of life, from infancy, fetal development to old age. However, during pregnancy and lactation, the risk of vitamin A deficiency increases as the need for this micronutrient increases significantly.
Infant nutrition affects not only the first years of life, but also plays an important role in the overall development and risk of disease in adults, including preventing prevent and limit the onset of chronic non-communicable diseases.
Vitamin A deficiency during pregnancy usually occurs in the last trimester of pregnancy because of the increase in maternal blood volume and fetal growth during the last weeks in the womb. In addition, the risk of vitamin A deficiency is often increased for pregnant women who do not consume vitamin A-rich foods, have an infection, diabetes or gestational diabetes.
Vitamin A deficiency is considered a health problem in many developing countries. The most common consequence is night blindness, which mostly occurs in Africa and Southeast Asia. Socio-economic factors are considered to be contributing causes of vitamin A deficiency during pregnancy. It is more common in poor countries, in regions and families with limited income, education, housing conditions and access to health services.
Nguy cơ thiếu hụt vitamin A thường tăng cao hơn đối với phụ nữ gặp tình trạng nhiễm trùng, đái tháo đường
5. Harm due to deficiency and excess of vitamin A during pregnancy
5.1. Vitamin A deficiency Vitamin A deficiency during pregnancy can lead to subclinical disorders such as decreased iron metabolism, altered cell differentiation, impaired immune response, or clinical disturbances such as: increased rates of disease, growth retardation, anemia and especially eye diseases, including night blindness, corneal ulceration, corneal molluscum contagiosum. In particular, night blindness is one of the first manifestations of vitamin A deficiency. In addition, the failure to fully meet vitamin A requirements during early fetal development can lead to serious abnormalities. , including early embryonic death.
Vitamin A deficiency in pregnant women can be one of the causes of fetal growth restriction, insulin resistance and glucose intolerance in adulthood. Furthermore, the condition is associated with diabetes and gestational diabetes.
5.2. Excess vitamin A Excessive vitamin A supplementation during pregnancy has been associated with teratogenicity in animal studies. Birth defects depend on excess vitamin A levels and the stage of pregnancy. The risk increases for the first 60 days after conception.
Isotretinoin is a drug containing one of several derivatives of vitamin A, commonly used to treat dermatological diseases, especially cystic acne and acne. However, this drug has a teratogenic potential and is contraindicated in pregnancy.
An increase in preformed vitamin A in maternal blood during the first trimester of pregnancy carries a risk of miscarriage and birth defects involving the cardiovascular and central nervous systems.
6. Vitamin A dose for pregnant women
Phụ nữ mang thai được khuyến khích bổ sung đầy đủ dinh dưỡng, tốt nhất thông qua chế độ ăn uống cân bằng, lành mạnh
Pregnant women are encouraged to get adequate nutrition, preferably through a healthy, balanced diet. Vitamin A deficiency for pregnant women should be given daily or weekly. According to current WHO guidelines, a single dose of vitamin A for pregnant women can be up to 10,000 units per day, or 25,000 units for a weekly dose.
A vitamin A supplement dose higher than 10,000 units daily (or 25,000 units weekly) is not recommended because its safety has not been proven, and there is a risk of teratogenicity if taken in the range of days 15 to 60 from conception.
In summary, vitamin A supplementation during pregnancy plays an extremely important role for the health of both the mother and the fetus. However, caution should be exercised in choosing a dose and consulting a doctor, to avoid overdoses that lead to side effects for the mother and baby.
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Reference source: NCBI; WHO
