Twenty-six pregnant women (10 in early pregnancy [6-17 weeks] and 16 in late pregnancy [21-37 weeks]) with increased urinary excretion of 3-hydroxyisovaleric acid (3-HIA), a finding suggestive of biotin deficiency, were randomly assigned to receive 300 mcg/day of biotin or placebo for 14 days. In both stages of pregnancy, 3-HIA excretion decreased significantly in the women who received biotin, but increased in those who received placebo.

Comment: Approximately 50% of pregnant women have elevated urinary excretion of 3-HIA which is suggestive of biotin deficiency. However, that abnormality could conceivably result from a pregnancy-induced change in the renal excretion of organic acids. The results of the present study suggest that increased 3-HIA excretion during pregnancy is, in fact, a reflection of biotin deficiency. The observation that biotin deficiency is common during the first trimester is cause for concern, since biotin deficiency in animals results in birth defects. Based on the results of this study, prenatal multivitamin formulas should probably contain biotin.

Mock DM, Quirk JG, Mock NI. Marginal biotin deficiency during normal pregnancy. Am J Clin Nutr 2002;75:295-299.

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