Maternal nutritional status has been shown to influence pregnancy outcomes. And the elevated maternal plasma homocysteine concentrations have been associated with adverse pregnancy outcomes. We investigated the effects of maternal serum levels of B vitamins and homocysteine, and the C677T MTHFR (5, 10-methylenetetrahydrofolate reductase) polymorphism on pregnancy outcomes. In 177 pregnant women of 24-28 wks of gestation, the MTHFR gene mutation, serum B vitamins and homocysteine concentrations were measured, and their pregnancy outcomes were investigated from medical records. The birth length, and 1- and 5-min Apgar scores of neonates in the T/T mothers were 45.4 $pm$ 9.3 cm, 7.6 $pm$ 3.2 and 8.5 $pm$ 3.8, respectively, which were significantly lower than those in the C/T (48.6 $pm$ 3.3 cm, 9.0 $pm$ 0.2, 10.0 $pm$ 0.2) or the C/C mothers (49.4 $pm$ 1.9 cm, 9.0 $pm$ 0.2, 10.0 $pm$ 0.0). The birth weight, birth length and the gestational age of neonates at delivery from hyperhomocysteinemic mothers whose homocysteine levels higher than 15 $mu$ mol were 2.5 $pm$ 1.3 kg, 43.9 $pm$ 9.0 cm, 35.4 $pm$ 6.3 wk, respectively, which were significant lower than those from normohomocysteinemic mothers (3.1 $pm$ 0.6 kg, 48.8 $pm$ 3.6 cm, 38.5 $pm$ 2.5 wk). The birth weight and birth length of neonates in mothers whose PLP levels were below the median were significantly lower than those from mothers with the PLP levels above the median. The 1- and 5-min Apgar scores of neonates were lower in mothers with the T/T MTHFR genotype than those with the C/T or C/C only when the serum PLP levels were below the median. The 1-, 5 min Apgar scores and birth length of neonates were lower in mothers with the T/T MTHFR genotype than those with the C/T or C/C only when the serum FMN levels were below the median. In conclusion, maternal B vitamin status, homocysteine and the C677T MTHFR genotype seem to have played an important role on pregnancy outcomes.