Vitamin A in Pregnancy: toxic or essential?

Does Your Prenatal Have Enough VitaminVitamin A is a critical nutrient for healthy pregnancy.

Sufficient vitamin A in pregnancy is needed for proper fetal skeletal and palette formation, proper development and regulation of the immune system, proper communication between the senses and the brain and proper lung development.

In animal tests vitamin A deficiency in pregnancy animals produced spontaneous abortion, eye defects, displacement of kidneys, testicles and ovaries, and deafness (see sources).

Is Vitamin A Toxic To The Fetus?

Pregnant women are often warned away from vitamin A-rich food such as liver and cod liver oil, because of concerns that excess vitamin A in pregnancy can cause birth defects in the fetus. For this reason, preformed vitamin A has even been taken out of some prenatal supplements, in favour of beta carotene, which is a pre cursor for vitamin A. 

Warnings about the possible teratogenic effects of vitamin A trace back to a 1995 study that found an increase in birth defects among mothers consuming more than 10,000IU a day of vitamin A supplements in early pregnancy (see sources below).

Guidelines and warnings about Vitamin A in pregnancy have been based on the results of this study, while a number of other studies have shown significantly more vitamin A (up to 50,000IU) to be safe, even beneficial, to the fetus (see sources),

One study concluded that consumption of between 20,000 and 40,000IU of vitamin A cut the risk of birth defect in half and this study showed no teratogenic effects at 10,000IUs

The current RDA for vitamin A during pregnancy is 2,600IU and there are some concerns that that might not be enough.

Given the importance of vitamin A to the developing fetus, it is important to check your prenatal vitamin for the presence of true vitamin A and eat vitamin A-rich foods such as liver, egg yolks shellfish and cod liver oil.  You can convert a class of phytonutrients called carotenoids into vitamin A, but this conversion is inefficient.  It is estimated that the conversion rate of beta carotene to vitamin A is about 6:1.  The conversion process takes place in the small intestine and requires the presence of bile.  Bile is released by the gall bladder in the presence of fat, so to improve your conversion, eat your beta carotene rich foods (like sweet potato and carrots) with some fat.   

Sources:

  • Luo T, Sakai Y, Wagner E, Dräger UC. Retinoids, eye development, and maturation of visual function. J Neurobiol.2006;66(7):677- 86.
  • Biesalski HK, Bohr D. Importance of vitamin-A for lung function and development. Mol Aspects Med. 2003;24:431-440.
  • Price WA. Nutrition and Physical Degeneration: 6th Edition. La Mesa, CA: Price-Pottenger Nutrition Foundation (2004) 334-339
  • Rothman KJ, Moore LL, Singer MR, Nguyen U-SDT, Mannino S, Milunsky A. Teratogenicity of High Vitamin A Intake.J Engl J Med. 1995;333:1369-73
  • Martínez-Frías ML, Salvador J. Epidemiological Aspects of Prenatal Exposure to High Doses of Vitamin A in Spain.Eur J Epidemiol. 1990;6(2):118-123.
  • Shaw GM, Wasserman CR, Block G. High maternal vitamin A intake and risk of anomalies of structures with cranial neural crest cell contribution. Lancet. 1996;347:899-900.
  •  Mills JL, Simpson JL, Cunningham GC, Conley MR, Rhoads GG. Am J Obstet Gynecol. 1997;177(1):31-6.
  • Martínez-Frías ML, Salvador J. Epidemiological Aspects of Prenatal Exposure to High Doses of Vitamin A in Spain.Eur J Epidemiol. 1990;6(2):118-123.

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