Relative validation of a quantitative FFQ for use in Brazilian pregnant women

Objective: To evaluate the ability of an FFQ, designed for use in Brazilian pregnant women, to estimate nutrient intakes during pregnancy. Design: A prospective study was conducted among 103 pregnant women attended by the Brazilian national health-care service. Food intake during pregnancy was evaluated by three 24 h dietary recalls (24hR), one per trimester of pregnancy, and also by two FFQ. The FFQ with eighty-five food items included questions about frequency of intake and portion sizes during two periods: the first 24 weeks of pregnancy and the pregnancy period as a whole. Deattenuated Pearson's correlation coefficients and joint classification into quartiles of nutrient intake were applied. Setting: Ribeirao Preto, Sao Paulo State, Brazil. Subjects: One hundred and three pregnant women, aged 18-35 years. Results: Acceptable correlation coefficients (r > 0.35) were found for Ca, K, Zn, Mg, fibre, vitamin C, niacin and folic acid for intake for the first 24 weeks; and for energy, lipids, protein, carbohydrate, Fe, K, Zn, fibre, vitamin B-6, riboflavin and niacin for the gestational period as a whole. A high proportion of study participants (>= 70 %) were categorized into the same or adjacent quartiles for estimated energy, carbohydrate, Ca, K, fibre, Zn, cholesterol, vitamin A, riboflavin, niacin, vitamin C, vitamin E and folic acid. Gross misclassification ranged from 2.3% (dietary fibre) to 12.5% (vitamin A, thiamin and SFA). Conclusions: The FFQ is a useful tool for assessing categories of nutrient intake during pregnancy, since a high proportion of women were classified into the same or adjacent quartiles.