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Objective: To provide the latest and most promising evidence on the prevalence and determinants for folic acid supplementation in pregnant women in Japan, including differences in prevalence between interview years and determinants across regions. Materials and methods: The study participants were enrolled from 15 regional centers across Japan between January 2011 and March 2014. Information on the use of folic acid supplementation before and during pregnancy and the characteristics of the participants were collected using questionnaires, medical chart reviews, and interviews by research coordinators. Results: Data for 91,538 women who provided sufficient data on folic acid supplementation were analyzed. The prevalence of adequate users was 8.0%, which, although low, tended to improve over the 4-year recruitment period. Various kinds of sociodemographic factors, lifestyle habits, and obstetrical and medication use history were significant and independent determinants for folic acid use. Associations between adequate preconception folic acid use and its major determinants tended to be similar across regions. Conclusions: Although the prevalence of adequate folic acid use was low, it increased from 2011 to 2014. Reproductive-aged women who have determinants for inadequate folic acid use should be informed about the need for preconception folic acid supplementation to help prevent neural tube defects.

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., (© 2018 Japanese Teratology Society.)

Objective: The aim of the study was to clarify the prevalence and determinants of inadequate use of folic acid supplementation in pregnant Japanese women., Methods: This study was part of the Japan Environment and Children's Study, a nationwide and government-funded birth cohort study. We collected information on the use of folic acid supplementation before and during pregnancy and characteristics of participants using self-administered questionnaire., Results: Among 9849 women who completed the data collection for this study, the prevalence of inadequate users was 92.6% of the total population and varied from 84.5% to 96.2% among regions. On the basis of multivariate logistic regression analysis, younger age, not married, lower family income, multipara, natural conception and no history of spontaneous abortion were found to be determinants for inadequate users of folic acid supplementation., Conclusion: Most Japanese pregnant women show inadequate folic acid supplementation use. Japanese women of child-bearing age need to be specifically informed about the need for periconceptional intake of folic acid to prevent neural tube defects.