| Summary: | <p>Abstract</p> <p>Background</p> <p>No validated dietary questionnaire for assessing folate and vitamin B<sub>12 </sub>intakes during pregnancy is available in Japan. We evaluated the validity and reproducibility of intakes of folate and vitamin B<sub>12 </sub>estimated from a self-administered diet history questionnaire (DHQ) in Japanese pregnant women.</p> <p>Methods</p> <p>A sample of 167 healthy subjects with singleton pregnancies in the second trimester was recruited at a private obstetric hospital in metropolitan Tokyo from June to October 2008 (n = 76), and at a university hospital in Tokyo from June 2010 to June 2011 (n = 91). The dietary intakes of folate and vitamin B<sub>12 </sub>were assessed using the DHQ. The serum concentrations of folate and vitamin B<sub>12 </sub>were measured as reference values in the validation study. To assess the reproducibility of the results, 58 pregnant women completed the DHQ twice within 4-5 week interval.</p> <p>Results</p> <p>Significantly positive correlations were found between energy-adjusted intakes and serum concentrations of folate and vitamin B<sub>12 </sub>(r = 0.286, <it>p </it>< 0.001 and r = 0.222, <it>p </it>= 0.004, respectively). After excluding the participants with nausea (n = 121), the correlation coefficient for vitamin B<sub>12 </sub>increased to 0.313 (<it>p </it>= 0.001). When participants were classified into quintiles based on intakes and serum concentrations of folate and vitamin B<sub>12 </sub>, approximately 60% were classified in the same or adjacent quintile. The intraclass correlation coefficients of the two-time DHQ were 0.725 for folate and 0.512 for vitamin B<sub>12 </sub>.</p> <p>Conclusion</p> <p>The present study indicated that the DHQ had acceptable validity and reproducibility for assessing folate and vitamin B<sub>12 </sub>intakes in Japanese pregnant women.</p>
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