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Molecular Cytogenetics (FISH) Vol. 13: Spring, 1996 |
In 1995, a study regarding possible adverse fetal effects of high dose retinol ingestion by women in early pregnancy was published by a group in Boston (1) . Based upon a review of this study as well as previous work concerning the teratogenicity of retinol, the Pregnancy RiskLine staff and medical director, John C. Carey, M.D., have concluded that any woman currently taking doses of vitamin A, as retinol or retinyl esters, up to 10,000 IUs per day should have NO concerns regarding increased teratogenic risk to her baby. This conclusion is shared by Oakley and Erickson at the CDC (2). Additionally, it is clear that beta-carotene as a source of vitamin A has not been shown to be teratogenic at ANY dose.
However, there are legitimate concerns about the relationship between prenatal use of vitamin A supplements in excess of 10,000 IU (as retinol or retinyl esters, not beta-carotene) and increasing risks for malformations. Additionally, it should be recognized that concurrent ingestion of retinol from high concentration vitamin A foods, especially frequent ingestion of liver, can contribute to the overall total amount of retinol consumed daily.
While the conclusions of the Boston study are basically in keeping with those above, one criticism of that study is the definition of malformation and the presumption that these defects are all the result of aberrant cranial neural crest cell migration. Retinoid embryopathy, a syndrome of anomalies involving the face, ear, heart, central nervous system and thymus, derives primarily from defects in migration of cranial neural crest cells. Previous experimental laboratory investigations and the clinically described retinoid embryopathy associated with other vitamin A analogs such as isotretinoin (Accutane), have linked high levels of exposure to these analogs (not beta-carotene) with abnormal migration of cranial neural crest cells early in embryonic development. It could be expected that vitamin A as retinol and retinyl esters may induce similar defects.
Unfortunately, the Boston investigators did not distinguish the cranial neural crest cell derived defects from others in their study. The research team included ALL CNS defects (except neural tube defects) as well as ALL heart defects in this category of cranial neural crest cell derived defects. Such broad categorization includes a number of defects (e.g. hydrocephalus), which may not be of cranial neural crest origin at all. Thus, possible misclassification confounds the conclusions drawn.
In summary, if a woman is taking a multivitamin, prenatal vitamin or Vitamin A supplements containing less than 10,000 IU (as retinol or retinyl), or beta-carotene at any dose, there is no evidence of an increase in the risk of malformations in her baby.
References:
Contributed by Lynn Martinez (UT)
The Genetic Drift Newsletter is not copyrighted. Readers are free to duplicate all or parts of its contents. The Genetic Drift Newsletter is published semiannually by the Mountain States Genetics Network for associates & those interested in Human Genetics. In accordance with accepted publication standards, we request acknowledgement in print of any article reproduced in another publication. The views expressed in the newsletter do not necessarily reflect local, state, or federal policy. For additional information, contact Carol Clericuzio, M.D., Editor, Department of Pediatrics, The University of New Mexico, Albuquerque, NM, 87131
Table Of Contents:
Molecular Cytogenetics (FISH)
Introduction & Basic Techniques
Applications of FISH Technology
FISH Applications in Cancer Cytogenetics
FISH in Microdeletion Syndromes
FISHing in Unknown Waters
Regulatory Issues and FISH
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