Beta-Carotene Supplementation During Pregnancy: What Key Roles Does It Play in Fetal Vision And Brain Development?

Pregnancy represents a critical window for fetal organ differentiation and the rapid development of the nervous and visual systems. Nutrient supply directly affects fetal development quality. As a safe precursor of vitamin A, beta-carotene differs from direct retinol supplementation. It is converted into vitamin A in the maternal body on demand, making it a vital fat-soluble nutrient for prenatal nutrition. Many expectant mothers only know to supplement folic acid, DHA, iron and calcium during pregnancy, yet tend to overlook vitamin A intake. Beta-carotene serves as a relatively safe dietary source to obtain vitamin A. Combining domestic nutritional reference standards and relevant research, this article analyzes the value of beta-carotene for fetal vision and brain development, and clarifies the safety limits for supplementation in pregnancy.

I. How Beta-Carotene Acts on Fetal Visual Development

Differentiation of fetal visual tissues including the retina, cornea and conjunctiva starts in the first trimester and continues to mature throughout the second and third trimesters. Vitamin A is indispensable for the development of visual cells. It participates in synthesizing rhodopsin in the retina, the core substance for sensing dim light and forming scotopic vision. Meanwhile, it maintains the integrity of ocular epithelial cells and supports normal corneal development.

According to the Chinese Dietary Reference Intakes (2013 Edition), the Recommended Nutrient Intake (RNI) of vitamin A for pregnant women is 770 μg RAE per day, higher than 700 μg RAE/day for ordinary adult women. The extra amount is used to build fetal eye tissues.

High-dose direct retinol supplementation carries risks of overdose and toxicity. The advantage of beta-carotene lies in its self-limiting conversion: the human body converts beta-carotene into active vitamin A only according to physiological demand. Excess beta-carotene will not be massively transformed into retinol, offering far better safety than retinol preparations. Long-term inadequate beta-carotene intake during pregnancy leads to depleted maternal vitamin A reserves, raising risks of poor fetal retinal development and impaired dark adaptation in newborns.

It should be clarified that beta-carotene is not equivalent to DHA. DHA mainly promotes the development of retinal photoreceptor cells and brain nerve cell membranes, while beta-carotene focuses on visual epithelial tissue and visual pigment synthesis. The two work synergistically and cannot replace one another. A balanced prenatal diet supplying both nutrients supports healthy development of the fetal visual system.

II. Key Value of Beta-Carotene for Fetal Brain and Nervous System Development

Vitamin A and its precursor beta-carotene play important roles in embryogenesis, neuronal migration and synapse formation. During neural tube closure in early pregnancy and cerebral cortex development in mid-to-late pregnancy, adequate vitamin A regulates neural stem cell differentiation and preserves the integrity of the central nervous epithelium.

The 2021 Expert Consensus on Clinical Application of Vitamin A and Vitamin D in Chinese Children states that maternal vitamin A nutritional status affects fetal nervous system development. Maternal vitamin A deficiency increases risks of fetal growth retardation and weakened immune function.

Vitamin A also participates in constructing mucosal immunity. The foundation of fetal mucosal immunity is established in utero. Sufficient vitamin A supports normal differentiation of epithelial cells in the fetal respiratory and digestive tracts, laying a foundation for defending against pathogens after birth. In addition, beta-carotene itself acts as an antioxidant. It scavenges free radicals in the mother's body, alleviates oxidative stress damage to the placenta, maintains normal placental blood and oxygen supply, and indirectly guarantees nutrient delivery to the fetal brain.

III. Beta-Carotene Supplementation in Pregnancy: Recommended Intake and Safety Boundaries

Pregnant women should obtain beta-carotene primarily from natural foods. The conversion rate of dietary beta-carotene: 12 μg of dietary all-trans beta-carotene ≈ 1 μg RAE. In practical terms, dark-colored vegetables and orange-yellow fruits can satisfy the needs of most pregnant women. Carrots, pumpkins, sweet potatoes, spinach, broccoli, mangoes and papayas are excellent sources.

The Chinese Dietary Guidelines (2022) recommend pregnant women consume 300–500 g of vegetables daily, with more than half being dark varieties. Adequate beta-carotene can be obtained through regular meals. Routine additional beta-carotene supplements are unnecessary for healthy pregnant women.

If an obstetrician or clinical dietitian assesses vitamin A deficiency and supplementation is required, dosage must be strictly controlled. It is critical to distinguish risks: food-derived beta-carotene almost never causes vitamin A toxicity. However, if a product contains retinol simultaneously, the combined intake from multiple sources may easily push total vitamin A over the limit. Excess active vitamin A (retinol) carries teratogenic risks; high retinol intake in early pregnancy may increase the chance of congenital malformations in the fetal craniofacial region and heart, which represents a red line in prenatal nutrition.

Although pure high-dose beta-carotene supplements do not directly trigger vitamin A poisoning, long-term mega-dose intake may cause carotenemia with skin yellowing in pregnant women. Some studies show insufficient evidence of safety benefits from high-dose purified beta-carotene supplementation in pregnancy. Self-administered long-term high-dose use is not recommended.

IV. Practical Advice for Pregnant Women

Prioritize food-based nutrition instead of blindly taking supplements. During prenatal check-ups, doctors may evaluate the need for extra supplementation based on serum retinol levels. Avoid self-purchasing high-dose adult beta-carotene health products.

Consume with oil. Beta-carotene is fat-soluble. Adding a small amount of olive oil or rapeseed oil when eating carrots, spinach and other vegetables improves absorption efficiency.

Do not stack multiple vitamin A-containing preparations, such as multivitamins, cod liver oil and beta-carotene capsules together. Combined intake may cause excessive total retinol.

Special populations: Pregnant women with gestational diabetes or hypothyroidism are more susceptible to carotenemia. Follow medical advice if supplementation is needed.

By converting into vitamin A, beta-carotene supports fetal visual tissue differentiation and nervous system development, making it an essential nutrient during pregnancy. Its biggest advantage is safe and controllable intake from dietary sources. Nevertheless, prenatal nutrition requires moderation and balance rather than excessive intake. For healthy expectant mothers, a diet rich in fruits and vegetables is the best way to obtain beta-carotene.