Preconception Maternal Iodine Status and Offspring Cognitive Function:
Condition: Cognitive Function
Study type: Observational

Summary: 
      Little is known about maternal iodine nutrition before conception and its relation with the
      child's cognitive function. Using samples and data from the Southampton Women's Survey,
      iodine measurements from urine collected before the mothers became pregnant will be related
      to cognitive function measures in the children at age 6-7 years.
    

Detailed description: 
      Adverse effects of severe maternal iodine deficiency in pregnancy on fetal brain development
      are well-established, but the effects of mild or moderate deficiency are not well understood.
      To date, most studies have examined iodine status in pregnancy; less is known about maternal
      iodine nutrition before conception, and this study aims to address that gap in information

      The Southampton Women's Survey (SWS) is a prospective study of mothers and children,
      established in 1998. A general population sample of 12,583 non-pregnant women, aged 20-34
      years resident in Southampton was recruited (1998-2002). All women were visited at home by a
      research nurse and characterised in detail, including assessments of diet, lifestyle and body
      composition. Between 1998 and 2007, 3158 of the SWS women became pregnant, and went on to
      deliver a live singleton infant. These women were followed up in through pregnancy and their
      children have been assessed in a number of follow-up studies in infancy and childhood. These
      have included repeated assessments of diet, anthropometry and body composition, as well as
      detailed functional measurements at specific ages, and are ongoing.

      At the 6-7 year assessment, the children's cognitive function was measured and this is the
      primary outcome.

      Spot urine samples were collected from the SWS women at clinic visits following their initial
      interviews (median 33 (IQR 15-87) days), in the period before conception. The time of day was
      recorded for each urine collection. Urine samples were split divided into aliquots on the day
      of collection. They were frozen and stored at -80⁰oC from the date of collection until being
      thawed and assayed for iodine and creatinine contents in 2016 by the Trace Element Unit,
      Southampton General NHS Trust Hospital, Southampton, UK.
    

Intervention name(s): Exposure is maternal iodine
Intervention type(s): Other
Intervention description(s): The exposure is preconception maternal iodine status There is no intervention in this observational study
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        The children are part of a cohort study that recruited their mothers before they were
        conceived. Women registered with a general practitioner in the Southampton area were
        recruited at ages 20-34 years when they were not pregnant. Those who subsequently became
        pregnant were followed through the pregnancy and then the children are being followed-up.
        This study focuses on iodine measures from the preconception recruitment and the follow-up
        in their homes of the children aged 6-7 years.
      
Biospecimen description: 
      Urine samples from women collected before they became pregnant