BIOTIN STATUS ASSESSED LONGITUDINALLY IN PREGNANT-WOMEN

This study assessed biotin nutritional status longitudinally during pr egnancy as judged by urinary excretion of biotin and biotin metabolite s and by serum concentration of biotin. 3-Hydroxyisovaleric acid excre tion was also assessed because increased excretion of that acid reflec ts decreased tissue activity of the biotin-dependent enzyme, methylcro tonyl-CoA carboxylase. Thirteen women provided untimed urine samples d uring both early and late pregnancy. Twelve nonpregnant women served a s controls. Biotin and metabolites were determined by a combined HPLC/ avidin-binding assay. 3-Hydroxyisovaleric acid was determined by gas c hromatography/mass spectrophotometry. Significance of changes from ear ly to late pregnancy was tested by paired t test; to compare nonpregna nt controls with early and late pregnancy, ANOVA was used. During earl y pregnancy, biotin excretion was not significantly different than con trols; however, 3-hydroxyisovaleric acid excretion was significantly i ncreased relative to controls (P < 0.0001) and was greater than the up per limit of normal in 9 of 13 women. From early to late pregnancy, bi otin excretion decreased in 10 of 13 women (P < 0.01); by late pregnan cy, biotin excretion was less than normal in six women. During late pr egnancy, 3-hydroxyisovaleric acid remained significantly increased rel ative to controls (P < 0.0001). Serum concentrations of biotin were si gnificantly greater than those of controls during early pregnancy (P < 0.0001) and decreased in each woman from early to late pregnancy (P < 0.0001). These data provide evidence that biotin status decreases dur ing pregnancy.