Association between repeated UICr measurements and IQ established

Primary endpoint: We will investigate whether mean child IQ levels differ according to mild-to-moderate iodine deficiency (classified using repeated urinary iodine measurements, see Tasks 4.2. and 4.4) by using multivariate linear regression models and combining the individual data from the three cohorts (see Task 4.1). Furthermore, we will investigate whether the iodine status is associated with the risk of learning disabilities (IQ<85) by using multivariate logistic regression analyses. (minimum odds ratio of 1.2 detectable as statistically significant). Secondary endpoints: Secondary studies will focus on the associations between repeated maternal UICcr measurements and child language development or autistic traits. The main analyses will investigate whether mean language development scores or autistic trait scores differ according to maternal iodine status by using multivariate linear regression models. Furthermore, we will investigate whether iodine status is associated with an increased risk of language delay and/or an increased risk of autistic traits by using multivariate logistic regression analyses. To study differential effects of specific pregnancy time-frames, UIC measurement analyses will be stratified according to gestational age. Neuropsychological outcomes will be analysed in relation to age of the child because differences in child neuropsychological development are likely to become more apparent with increasing age. We will furthermore investigate differential effects according to maternal thyroid function, socioeconomic status (SES) and child gender. Because iodine excess has also been associated with thyroid dysfunction, we will also explore neuropsychological development across the whole distribution of UICcr.