Proposal for supplemental intake of folic acid to reduce the risk of neural tube defects

Evaluating folic acid supplementation among Japanese pregnant women with dietary intake of folic acid lower than 480 µg per day: results from TMM BirThree Cohort Study

Objective: In Japan, supplementation with 400 µg of folic acid per day is recommended for women who are planning to get pregnant to decrease the risk of their babies getting neural tube defects (NTD). However, the proportion of women who have taken folic acid supplements before conception is low among Japanese pregnant women. In addition, the dietary intake of folic acid has not yet reached the government recommended dietary intake levels (480 µg per day). This study aimed to clarify the prevalence and determinants of adequate folic acid supplements among Japanese pregnant women with dietary folic acid intake lower than 480 µg per day.Methods: This cross-sectional study was a part of the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study. We collected information on folic acid supplements before conception, sociological/lifestyle characteristics, and food consumption. The primary outcome was the use of folic acid supplements (adequate or inadequate, based on the timing of initiation of folic acid supplements). Multiple logistic regression analysis was used to examine the association between sociological/lifestyle characteristics and the adequate intake of folic acid supplements.Results: Among the 11,562 pregnant women who took lower than 480 µg per day of folic acid from food, the prevalence of adequate users was 18.0%. Pregnant women who reported adequate use of folic acid supplements were more likely to be older and educated; and reported higher household income, and history of fertility treatment. Conversely, they were less likely to be ever or current smokers and multipara.Conclusion: This study found that the prevalence of folic acid supplements use for the prevention of NTD among Japanese pregnant women was still low.

Real prevalence of neural tube defects in Japan: How many of such pregnancies have been terminated?

The vital role of folic acid is to reduce the risk of having a neonate afflicted with neural tube defects. The prevalence of neural tube defects (myelomeningocele and anencephaly) has been reported in an incomplete form over the last 40 years in Japan. We aimed to evaluate the total number of neural tube defects including those delivered or terminated, to clarify the proportion of those terminated, and to internationally compare their prevalence. Through information on >311 000 deliveries obtained from 262 hospitals/clinics for 2 years of 2014 and 2015, we identified that the rate of total neural tube defects (termination of pregnancy, live births and stillbirths) was 8.29 per 10 000 deliveries for the year 2014 and was 8.72 for 2015, which were 1.5 and 1.6 times higher than the respective values (live births and stillbirths) reported. It is also observed that the ratio of the total number of myelomeningocele (termination of pregnancy, live births, and stillbirths) to that of anencephaly was approximately 1:1.2, that a half of pregnancies afflicted with neural tube defects were terminated, and that the proportion of termination of pregnancy due to myelomeningocele and due to anencephaly was 20% and 80%, respectively. Internationally, the real prevalence of neural tube defects in Japan was comparatively high, ranking fifth among the seven developed countries. In conclusion, the real prevalence of total neural tube defects was approximately 1.5 times higher than that currently reported by the Japan Association of Obstetricians and Gynecologists.

Preconception folic acid supplementation use and the occurrence of neural tube defects in Japan: A nationwide birth cohort study of the Japan Environment and Children's Study

We evaluated the relationship between preconception folic acid supplementation and the occurrence of neural tube defects (NTDs) in offspring, using data from the Japan Environment and Children's Study (a nationwide prospective birth cohort study) database. Of 92 269 participants with single pregnancies, 74 cases (offspring or fetuses) had NTDs, including 32 cases of spina bifida, 24 cases of anencephaly, and 19 cases of encephalocele. A total of 7634 participants (8.27%) used preconception folic acid supplementation, and of these, 621 (0.67%) also took in dietary folic acid at ≥480 μg/day. Multivariate logistic regression analyses demonstrated no association between preconception folic acid supplementation and NTDs in offspring or fetuses (odds ratio [OR] 0.622; 95% confidence interval [CI]: 0.226-1.713). Moreover, the participants who combined preconception folic acid supplement use with dietary folic acid intake ≥480 μg/day demonstrated no incidence of NTDs in offspring or fetuses. Our analysis is limited by the absence of the data on the daily amount of supplementary folic acid intake, requiring careful attention to the interpretation. Additional surveys are required in Japan to resolve those limitations for further comprehensive assessment.