There is concern that excessive quantities of vitamin A may have a teratogenic effect. Two metabolites (trans-retinoic acid - RA, tretinoin, and 13-cis retinoic acid - CRA, isotretinoin) are believed to be responsible for this.
- there are no convincing cases of a foetus being deformed as a result of excessive vitamin A intake from food
- nevertheless, pregnant women in the UK have been warned against eating liver
- "women can be assured that eating a balanced diet which does not include liver will provide an adequate vitamin A intake"
- "there is no reason to change the normal provision of vitamin A supplementation during pregnancy, under the supervision of the general practitioner, midwife or antenatal clinic, provided women are advised of the importance of keeping to the recommended dose"
There have been reports of undesirable side-effects following massive doses of vitamin A supplements in infancy.
NICE state that (2):
- pregnant women should be informed that vitamin A supplementation (intake greater than 700 micrograms) might be teratogenic and therefore it should be avoided
- pregnant women should be informed that as liver and liver products may also contain high levels of vitamin A, consumption of these products should also be avoided
Reference:
- Bates CJ. Vitamin A. Lancet 1995;345:31-35.
- NICE (2008). Antenatal care.