Methodological challenges when monitoring the diet of pregnant women in a large study: experiences from the Norwegian Mother and Child Cohort Study (MoBa)

Abstract

The aim of this article is to describe the main methodological challenges in the monitoring of dietary intake in the Norwegian Mother and Child Cohort Study (MoBa), a pregnancy cohort aiming to include 100 000 participants. The overall challenge was to record dietary patterns in sufficient detail to support future testing of a broad range of hypotheses, while at the same time limiting the burden on the participants. The main questions to be answered were: which dietary method to choose, when in pregnancy to ask, which time period should the questions cover, which diet questions to include, how to perform a validation study, and how to handle uncertainties in the reporting. Our decisions were as follows: using a semi-quantitative food frequency questionnaire (FFQ) (in use from 1 March 2002), letting the participants answer in mid-pregnancy, and asking the mother what she has eaten since she became pregnant. The questions make it possible to estimate intake of food supplements, antioxidants and environmental contaminants in the future. Misreporting is handled by consistency checks. Reports with a calculated daily energy intake of <4.5 and >20 MJ day(-1) are excluded, about 1% in each end of the scale. A validation study confirmed that the included intakes are realistic. The outcome of our methodological choices indicates that our FFQ strikes a reasonable balance between conflicting methodological and scientific interests, and that our approach therefore may be of use to others planning to monitor diet in pregnancy cohorts.

Pregnancy‐Related Risk Factors Are Associated With a Significant Burden of Treated Hypertension Within 10 Years of Delivery: Findings From a Population‐Based Norwegian Cohort

“…At 6 months after delivery, another questionnaire ascertained breastfeeding, changes in weight from prepregnancy weight, and smoking status. Dietary intake was obtained from a semiquantitative food frequency questionnaire developed specifically for the MoBa, and administered in the 22nd week of pregnancy 29. The MoBa food frequency questionnaire has been validated in substudies using a 4‐day weighted food diary, motion sensors, and biological markers 30, 31.…”

Exploration of biomarkers for total fish intake in pregnant Norwegian women

“…Validation study subjects and design The present study was part of a validation study of a new FFQ developed for use in the MoBa study (20) . Other results of the validation study have been published elsewhere (21) .…”

Prenatal mercury exposure and infant birth weight in the Norwegian Mother and Child Cohort Study

“…The dietary data used in the present study were collected from February 2002 to November 2009. The FFQ is a semi-quantitative questionnaire designed to capture dietary habits and intake of dietary supplements during the first four to five months of pregnancy (32) . The FFQ included questions about intake of 255 food items with special emphasis on various fish and seafood items.…”

“…In MoBa, a large, prospective pregnancy cohort, women answered a detailed FFQ in mid-pregnancy. The dietary data provide a unique opportunity to explore dietary exposures to a wide range of foods, nutrients and contaminants and to examine associations between maternal diet and health outcomes in the children (32) . The aims of the present study were: (i) to estimate the dietary exposure to Hg in MoBa; and (ii) to examine if maternal dietary Hg exposure was associated with infant birth weight.…”