Dietary folate intake during pregnancy and birth weight in Japan

BACKGROUND: Inadequate folate status has been associated with many negative reproductive outcomes, such as neural tube defects (NTD), low birth weight and placental abruption. AIM OF THE STUDY: The objectives of this study were to evaluate the levels of dietary folate intake during pregnancy in Japanese women and the subsequent birth weight of their babies. METHODS: A longitudinal prospective study was conducted with 197 women with a singleton pregnancy in 2005. Dietary folate was investigated 3 times: in the first trimester at 12 weeks, in the second trimester at 20 weeks and in third trimester at 32 weeks using a diet history questionnaire (DHQ). Non fasting blood samples were collected from the women for measurement of homocysteine, hemoglobin, ferritin, unbound iron-binding capacity (UIBC) and total iron-binding capacity (TIBC). RESULTS: Energy intake increased as pregnancy advanced, but not significantly. The daily intake of folate increased from 248.5 +/- 113.1 microg/d in the first trimester to 275.4 +/- 100.2 microg/d in the third trimester (P = 0.04). This was well below the recommended level of 440 microg/d and only 10% of mothers were above the levels. In the third trimester, plasma homocysteine concentration was significantly higher in the low folate group of less than 250 microg/d (P = 0.02), but not the first and second trimesters. Dietary folate intake and plasma homocysteine concentrations were not likely to be predictors of birth weight in our subjects. CONCLUSIONS: Our study shows that Japanese women's energy and folate intakes do not meet their energy needs during pregnancy and are at an extremely low recommended dietary allowance level throughout pregnancy.