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VITAMIN A AND BIRTH DEFECTS Animal models and clinical experience with the vitamin A analogue isotretinoin suggest that high doses of vitamin A may cause birth defects, particularly malformations of structures derived from cranial neural crest cells.

To examine this relationship, researchers at Boston University School of Medicine and the California Birth Defects Monitoring Program used data from the Slone Epidemiology Unit Birth Defects Study, an ongoing surveillance program conducted in Boston, Philadelphia, Toronto, and five Iowa counties between 1976 and 1985. Cases were 2,658 infants with malformations of structures derived at least in part from the cranial neural crest, and controls were 2,609 control infants with other birth defects. Among many other questions, mothers of the infants were asked about their use of vitamin A supplements (defined as vitamin A alone, vitamins A and D together, or fish liver oils) and multivitamins (including "prenatal" vitamins) during the first three months of pregnancy. They were not asked about the doses taken.

It was found that 0.6% of case mothers and 0.3% of control mothers had taken vitamin A supplements during the first trimester of pregnancy. Thus women who used these supplements appeared to have a twofold increased risk of giving birth to infants with the types of defects investigated here. However, the relative risk estimates were not statistically significant, and thus the data are also compatible with no association. The lack of information on size of the vitamin A dose and the small number of exposed individuals also limit the interpretation of these findings.

Approximately 50% of both case and control mothers took multivitamins that included vitamin A during the first trimester of pregnancy. Relative risks approximated unity, and 95% confidence intervals excluded even small increases of risk attributable to these supplements.

"The results of this study strongly suggest that daily intake of vitamin A-containing multivitamin supplements, including 'prenatal' vitamins, does not increase the risk of malformations involving structures derived, at least in part, from cranial neural crest cells.c

Martha M WEler et al, Maternal Vitamin A Supplementation in Relation to Selected Birth Defencts, Teratology 42(5):497-503 (Nov 1990) [Correspondence: Martha M Werler, Slone Epidemiology Unit, School of Public Health, Boston University School of Medicine, Brookline MA 02146]