Quick answer

NIH says too much preformed vitamin A in pregnancy can cause birth defects. It reports that experts advise women who are or might be pregnant not to take more than 3,000 mcg RAE (10,000 IU) a day from supplements. Beta-carotene is not known to cause this problem, and women 19 and older need 770 mcg RAE a day.^1,2

Key facts

The upper limit for preformed vitamin A is 3,000 mcg a day for adults 19 and older and 2,800 mcg for teens 14 to 18, in pregnancy too, counting food, drinks and supplements.^1,2
NIH names malformations of the eye, skull, lungs and heart among the birth defects from too much preformed vitamin A.^1,2
In a study of 22,748 pregnant women, supplemental vitamin A above 10,000 IU a day went with about 4.8 times the rate of one group of birth defects, with an apparent threshold near that amount.³
Beta-carotene, the plant form, is not known to cause birth defects or reproductive toxicity, unlike preformed vitamin A.¹
Prenatal supplements generally provide no vitamin A in the form of retinol.⁴

What NIH says about vitamin A and birth defects

NIH's fact sheet for consumers puts it plainly: taking too much preformed vitamin A while pregnant can cause birth defects, and anyone who is or might be pregnant or breastfeeding should not take high-dose supplements of preformed vitamin A. The fact sheet for health professionals says the same and gives the number experts use.^1,2

Too much preformed vitamin A in pregnancy can cause birth defects, including malformations of the eye, skull, lungs and heart.^1,2

It reports that experts advise women who are or might be pregnant not to take more than 3,000 mcg RAE (10,000 IU) a day of vitamin A as supplements. MedlinePlus agrees that large doses of vitamin A in pregnant women can cause birth defects.^1,5

The upper limit for preformed vitamin A is 3,000 mcg a day for adults 19 and older, including in pregnancy and while breastfeeding, and 2,800 mcg for teens 14 to 18. It counts food, drinks and supplements, and it is lower for children: 600 mcg up to age 3, 900 mcg at 4 to 8 and 1,700 mcg at 9 to 13. The limits do not apply to people taking vitamin A under a doctor's care. No upper limit is set for beta-carotene, but the Food and Nutrition Board advises against beta-carotene supplements for the general population except as a source of vitamin A.^1,2

Does the form of vitamin A matter in pregnancy?

Yes, according to NIH. The upper limit applies to preformed vitamin A, which is retinol and its esters such as retinyl palmitate, and to products from animal sources. The plant form, beta-carotene, is not known to be teratogenic or to cause reproductive toxicity, and no upper limit is set for it.¹

Many supplements mix the two. NIH's example is a supplement labeled 3,000 mcg RAE of which 60% comes from beta-carotene, which gives 1,200 mcg RAE of preformed vitamin A. The label's percentage from retinol or retinyl ester is what counts toward the limit.¹

Prenatal supplements generally provide no vitamin A in the form of retinol.⁴

What studies found on high vitamin A intake in pregnancy

The best-known study followed 22,748 pregnant women, of whom 339 had babies with birth defects, 121 at sites that form from the cranial neural crest. Babies of women who took more than 10,000 IU of supplemental vitamin A a day had about 4.8 times the rate of those defects of babies whose mothers took 5,000 IU or less a day. The excess was concentrated in women who took high amounts before the seventh week of pregnancy.³

It was an observational study, so it shows an association and not proof of cause. NIH says its upper limits were set from the amounts linked to liver abnormalities, birth defects and toxic effects in infants and children, and that some retinoid medicines, such as isotretinoin, can also cause birth defects.¹

A Cochrane review of 19 trials with over 310,000 women looked at vitamin A given in pregnancy, mostly in places where deficiency is common. Its main results concern deaths, night blindness, anemia and infection, so it does not settle the question of high doses in well-nourished women.⁶

Who should ask a doctor about vitamin A in pregnancy

Anyone who is or might be pregnant and takes a vitamin A, fish liver oil or multivitamin product, who should ask their doctor or pharmacist how much preformed vitamin A it holds.^1,2
Anyone who also eats liver often, since liver is among the foods highest in preformed vitamin A.¹
Anyone taking isotretinoin or another retinoid medicine, whose labels and pharmacists give separate warnings about pregnancy.^1,7
Anyone who is unsure whether a product's vitamin A is retinol or beta-carotene, which is stated on the Supplement Facts panel.¹

Questions people ask

Is vitamin A palmitate safe during pregnancy?

Retinyl palmitate is a preformed form of vitamin A, so the 3,000 mcg a day upper limit applies to it. NIH reports experts advise women who are or might be pregnant not to take high-dose supplements. Ask your doctor.¹

Is vitamin A retinol safe during pregnancy?

Retinol is preformed vitamin A. NIH says too much of it in pregnancy can cause birth defects, including malformations of the eye, skull, lungs and heart. Ask your doctor about any product with retinol.^1,2

Is a vitamin A supplement okay during pregnancy?

NIH gives 770 mcg RAE a day for women 19 and older in pregnancy and an upper limit of 3,000 mcg of preformed vitamin A. Ask your doctor how that compares with your prenatal and any other product.¹

Is beta-carotene a problem in pregnancy?

NIH says beta-carotene is not known to be teratogenic or to cause reproductive toxicity, unlike preformed vitamin A. It has a separate caution: in two large trials, smokers who took 20 to 30 mg a day of beta-carotene had more lung cancer. Ask your doctor about any supplement.^1,4

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This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.