Most Japanese women do not consume the estimated average requirement of vitamin B6 (1.7 mg/d) during pregnancy. Nevertheless, these deficiencies are not reported. We investigated a nutritional biomarker of vitamin B6 in pregnant Japanese women as well as their vitamin B6 intakes. Vitamin B6 intakes in the first, second, and third trimesters of pregnancy, and 1 mo after delivery were 0.79±0.61 (n=56), 0.81±0.29 (n=71), 0.90±0.35 (n=92), and 1.00±0.31 (n=44) mg/d, respectively. Plasma pyridoxal 5'-phosphate (PLP) concentrations in the first, second, and third trimesters of pregnancy, and 1 mo after delivery were 57.1±27.6 (n=56), 23.3±16.7 (n=71), 18.3±12.5 (n=92), and 43.9±33.4 (n=44) nmol/L, respectively. The plasma concentrations significantly decreased in the second and third trimesters of pregnancy compared to values from the first trimester (p<0.05), and these concentrations returned to the values of the first trimester of pregnancy 1 mo after birth.