Validity of the Willett food frequency questionnaire in assessing the iron intake of French-Canadian pregnant women.

OBJECTIVE

Maternal intake is crucial to pregnancy outcomes. Evidence shows that both nutrient deficiency and excess can have adverse effects. In pregnancy, changes in iron metabolism occur; therefore, dietary reference intakes increase to support expansion of red cells and maternal-fetal transfer of iron. Appropriate and valid assessment tools are required to investigate nutritional concerns in mothers with and without gestational diabetes mellitus (GDM). The objective of this study was to assess the Willett food frequency questionnaire (FFQ) to assess iron intake in women with (n = 15) and without (n = 45) GDM.

METHODS

To validate the modified FFQ, estimated total iron intake during the third trimester was compared with biomarkers of iron status such as serum ferritin, soluble transferrin receptor (sTfR), and the sTfR:F index at delivery. Data were tested for normality using the D'Agostino-Pearson test. Differences between groups were tested using t tests or Mann-Whitney tests. Correlations were tested using Spearman's ρ. Significance was set at P < 0.05.

RESULTS

Significant crude and energy-adjusted serum ferritin and total iron intake were related (ρ = 0.30; P < 0.05) in women without GDM. Serum ferritin, sTfR, and the sTfR:F index were different (P < 0.05) between women with intakes above and below the recommended levels. Cross-classification showed agreement between methods in mothers with and without GDM; on average, 63% of the women were classified into the same or adjacent quartile when ranked by FFQ and iron status.

CONCLUSION

These findings suggest the Willett FFQ is a good tool for assessing total iron intake of French-Canadian pregnant women.