Validation of a novel method for retrospectively estimating nutrient intake during pregnancy using a semi-quantitative food frequency questionnaire.

Case control studies evaluating the relationship between dietary intake of specific nutrients and risk of congenital, neonatal or early childhood disease require the ability to rank relative maternal dietary intake during pregnancy. Such studies are limited by the lack of validated instruments for assessing gestational dietary intake several years post-partum. This study aims to validate a semi-quantitative interview-administered food frequency questionnaire (FFQ) for retrospectively estimating nutrient intake at two critical time points during pregnancy. The FFQ was administered to women (N = 84), who 4-6 years earlier had participated in a prospective study to evaluate dietary intake during pregnancy. The FFQ queried participants about intake during the previous month (FFQ-month). This was then used as a reference point to estimate consumption by trimester (FFQ-pregnancy). The resulting data were compared to data collected during the original study from two 24-h recalls (24 h-original) using Spearman correlation and Wilcoxon sign-rank-test. Total energy intake as estimated by the retrospective and original instruments did not differ and was only weakly correlated in the trimesters (1st and 3rd) as a whole (r = 0.18-32), though more strongly correlated when restricted to the first half of the 1st trimester (r = 0.32) and later half of the 3rd trimester (r = 0.87). After energy adjustment, correlation between the 24hR-original and FFQ-pregnancy in the 3rd trimester were r = 0.25 (P < 0.05) for dietary intake of vitamin A, and r = 0.26 (P < 0.05) for folate, and r = 0.23-0.77 (P < 0.005) for folate, and vitamins A, B6 and B12 in the 1st and 3rd trimester after including vitamin supplement intake. The FFQ-pregnancy provides a consistent estimate of maternal intake of key micronutrients during pregnancy and permits accurate ranking of intake 4-6 years post-partum.