**2.3 Measurement of nutrition-related factors ("exposures")**

#### **2.3.1 Questionnaires**

A questionnaire summarising weekly diaries were filled out when the children were 3, 6, 9 and 12 months old, and annually thereafter. The questionnaires include for examples detailed information about dietary habits of the mother and the child (detailed information about diet for the mother as long as she breast-fed and intake of specific food items, etc.). Since few studies have been conducted on children's diet in Norway, new dietary questions had to be developed for both the MIDIA and the MoBa study. Validation of various aspects of dietary habits of pregnant women has recently been undertaken within the MoBa study. Blood samples and questionnaires from MIDIA can be used to assess validity of relevant information in childhood (Brantsæter et al., 2007a, 2007b, 2008, 2009; Willett, 1998; Serdula et al., 2001).
