JMIR Publications

ABSTRACT

Background:

Thyroid dysfunction is associated with cognitive impairment, mood disturbance, and postnatal depression. Sufficient thyroid hormone synthesis requires adequate intake of iodine, selenium and iron. Iodine deficiency was historically a problem for New Zealand, and initiatives were introduced to overcome the problem: 1) mandatory fortification of all bread (except organic) with iodised salt (2009); and 2) provision of subsidised iodine supplements for pregnant and breastfeeding women (2010). Subsequent to these initiatives most adults and children have adequate iodine status, however status among breastfeeding women and their infants remains unclear. This paper outlines the methodology of the Mother and Infant Nutrition Investigation (MINI) study: an observational longitudinal cohort study of breastfeeding women and their infants.

Objective:

This study will determine: a) women’s iodine intake and status among supplement users and non-users; b) women’s intake and status of iodine, selenium, and iron relating to thyroid function; c) associations between women’s selenium status, thyroid function and postnatal depression; d) infants’ iodine and selenium status relating to first-year neurodevelopment.

Methods:

Breastfeeding women aged over 16 years with a healthy term singleton infant recruited from Manawatu, New Zealand. Participants attended at 3, 6 and 12 months postpartum. Maternal questionnaires investigated supplement use before and after birth, iodine knowledge, and demographic information. Dietary assessment, with urine, blood and breastmilk samples, were taken to measure iodine, selenium and iron intake/status. The Edinburgh Postnatal Depression Scale was used repeatedly to screen for postnatal depression. Thyroid hormones (free T3, free T4, TSH, Tg and anti-Tg and anti-TPO) were measured in blood samples and thyroid gland volume measured by ultrasound at 6 months. Infant iodine and selenium concentrations were determined in urine. Ages and Stages Questionnaires was used to assess infants’ development 4, 8 and 12 months.

Results:

Data collection has been completed.

Conclusions:

This study will provide data on the current iodine status of breastfeeding women. It will also provide a greater understanding of the three essential minerals required for optimal thyroid function among breastfeeding women. This prospective longitudinal design allows opportunities to examine women’s mental health and infant neurodevelopment throughout their first year, a crucial time for both mothers and their infants. Clinical Trial: ACTRN12615001028594