Folate and Vitamin B12 are essential nutrients important during pregnancy. This study was conducted to evaluate the folate and vitamin B12 nutritional status of Korean pregnant women and to investigate the relationship between maternal-umbilical cord serum folate and vitamin B12 levels and pregnancy outcomes. Dietary intakes of the pregnant women were estimated by 24 hour-recall (3 times). Serum folate and vitamin B12 levels in maternal blood and umbilical cord of 27 pregnant women at 1'st-, 2'nd-, 3'rd- trimester and delivery were measured by RIA (radioimmuno assay), respectively. Means of folate and vitamin B12 intake were 283.53 +/- 58.01 microgram/day and 2.99 +/- 1.32 mg/day, respectively. Maternal mean serum folate levels of the trimester and delivery were 9.75 +/- 3.60 ng/ml, 10.46 +/- 4.63 ng/ml, 10.71 +/- 4.14 ng/ml and 15.05 +/- 7.04 ng/ml. Those maternal levels were significantly lower than that of umbilical cord blood (23.99 +/- 9.42 ng/ml). Serum vitamin B12 levels of maternal trimester and delivery were 479.07 +/- 137.56 pg/ml, 310.96 +/- 137.56 pg/ml, 308.22 +/- 74.65 pg/ml, and 295.67 +/- 93.36 pg/ml, which were significantly lower than those of umbilical cord blood (500.13 +/- 185.60 ng/ml). This finding indicates that the uptake of folate and vitamin B12 in the fetus may be due to an active placental transport mechanism. Maternal serum level correlated positively with those of umbilical cord blood, showing that folate and vitamin B12 concentration of umbilical cord blood might be affected by maternal status. There was no significant correlation between the serum folate levels in maternal-umbilical cord blood and the pregnancy outcomes. However, maternal vitamin B12 level at 1'st trimester was significant positive correlation between the gestational age except for birth weight and weight gain.