Vitamin A is the clearest example on this site of why 'natural versus supplement' is sometimes a real distinction and not marketing. Two forms, very different safety profiles, and the difference genuinely matters in pregnancy.
We are leading with the unpleasant half, because getting this one backwards is the kind of mistake that is hard to undo.
What is the actual risk?
It comes from preformed vitamin A, also called retinol, and it comes from the fact that it is fat-soluble and accumulates rather than flushing.
Excess retinol (preformed vitamin A) can lead to liver toxicity and fetal abnormalities because it is efficiently absorbed, fat-soluble, and stored rather than excreted.
Stated in a health authority's guidance
Clinical review pending
A health authority states this in its published guidance.
Preformed vitamin A is efficiently absorbed in the small intestine and stored in the liver, where it can accumulate and lead to toxicity... an excess of retinol can lead to liver toxicity and fetal abnormalities.
Total daily vitamin A from supplements should be kept under 10,000 IU during pregnancy; if higher, cut back or switch supplements.
Stated in a health authority's guidance
Clinical review pending
A health authority states this in its published guidance.
ULs for Preformed Vitamin A: 19+ years Pregnancy 3,000 mcg... The FNB based these ULs on the amounts associated with... teratogenic effects... 1 IU retinol = 0.3 mcg RAE
This is the question people ask last and should ask first, because skincare is where most women encounter retinoids daily without thinking of them as a supplement at all.
Pregnant women should stop using topical retinoids and should not take any vitamin A supplement unless a doctor recommends it.
Multiple health authorities agree
Clinical review pending
More than one independent health authority states this.
Although topical retinoids are not recommended during pregnancy as a precaution... Pregnant women should not ingest excessive vitamin A. They should consult clinicians before taking any supplements and must never use systemic retinoids due to the risk of severe teratogenic effects.
No, and here is the good news the first half of this page has been holding back. Beta-carotene from vegetables does not behave like retinol, because your body converts only what it needs.
The worst it does is cosmetic, temporary, and mildly funny.
Natural vitamin A from beta-carotene in vegetables does not cause vitamin A's harmful fetal effects and can be eaten without limit.
Stated in a health authority's guidance
Clinical review pending
A health authority states this in its published guidance.
Unlike preformed vitamin A, beta-carotene is not known to be teratogenic or lead to reproductive toxicity... The most common effect of long-term, excess beta-carotene is carotenodermia, a harmless condition in which the skin becomes yellow-orange.
Vitamins D, E and K sit in the same absorption category as A, and vitamin C does not, but it turns up in the same conversation about prenatal supplement labels. The published figures are below.
Pregnant women should get 15 mcg (600 IU) of vitamin D per day, obtainable from fatty fish, eggs, and fortified foods.
Stated in a health authority's guidance
Clinical review pending
A health authority states this in its published guidance.
RDA table: 19-50 years — Pregnancy 15 mcg (600 IU), Lactation 15 mcg (600 IU)... 'Vitamin D is found naturally in a few foods, such as the flesh of fatty fish, fish liver oils, beef liver, egg yolks, and cheese. In American diets, fortified foods... provide most of the vitamin D.'
The RDA for vitamin E is 15 mg (22 IU) daily; deficiency is rare but more likely with digestive/fat-malabsorption disorders, with signs including retinopathy, peripheral neuropathy, ataxia, and decreased immune function.
Stated in a health authority's guidance
Clinical review pending
A health authority states this in its published guidance.
RDA 14+ years: 15 mg ... 15 mg of natural alpha-tocopherol would equal 22.4 IU ... Frank vitamin E deficiency is rare... people who have fat malabsorption disorders are more likely to become deficient... Deficiency symptoms include peripheral neuropathy, ataxia, skeletal myopathy, retinopathy, and impairment of the imm…
Vitamin E deficiency is rare but more likely with digestive disorders or fat malabsorption; signs are retinopathy, ataxia, and decreased immune function.
Stated in a health authority's guidance
Clinical review pending
A health authority states this in its published guidance.
"Frank vitamin E deficiency is rare... people with fat-malabsorption disorders are more likely to become deficient." "Deficiency symptoms include peripheral neuropathy, ataxia, skeletal myopathy, retinopathy, and impairment of the immune response."
Prenatal supplements with under 2,000 mg vitamin C per serving are most likely fine to continue because vitamin C is water-soluble and modest excess is excreted in urine.
Stated in a health authority's guidance
Clinical review pending
A health authority states this in its published guidance.
UL table: 19+ years (incl. Pregnancy) 2,000 mg... 'vitamin C... is a water-soluble vitamin'... 'absorbed, unmetabolized ascorbic acid is excreted in the urine'... 'In general, vitamin C has low toxicity'