Abstract
An adequate intake of iodine during pregnancy is necessary for normal growth and brain development of the fetus. Studies conducted in the 1990’s and early 2000’s have shown that pregnant women in New Zealand have an inadequate iodine status. In 2009 the government introduced the mandatory fortification of bread with iodised salt to combat iodine deficiency in the New Zealand population. In 2010 the Ministry of Health recommended that all women planning a pregnancy, pregnant or breastfeeding take an iodine supplement. The aim of this study was to determine if the mandatory fortification of bread with iodised salt with or without the addition of iodine supplements in pregnancy has improved the iodine status of pregnant New Zealand women.
A cross-sectional study of pregnant women living in Hamilton, New Zealand was conducted from April to September 2012. Participants were recruited through antenatal clinics and by advertisement. All participants were asked to provide a casual urine sample used for the determination of urinary iodine concentration (UIC) and complete a questionnaire used to obtain socio-demographic information and the frequency of consumption of iodine-containing foods including fortified bread and dietary supplements.
A total of 118 pregnant women took part in the study. The median (25th, 75th) UIC of the women was 108 (68,169) µg/L, which falls below the WHO/ICCIDD/UNICEF cut-off of 150µg/L indicating inadequate iodine status in these pregnant women. There was no significant difference between the UIC of women consuming iodine supplements in pregnancy compared to those who were not (p=0.187); women who reported taking an iodine supplement with > 200μg of iodine had a UIC of 148μg/L compared to 102μg/L found in women taking an iodine supplement with <200μg of iodine and 100μg/L for women taking no supplements or supplements that did not contain iodine. Furthermore, the estimated dietary iodine intake obtained from the iodine-specific FFQ was 115µg/day, which is less than the recommended daily intake of iodine of 220µg/day for pregnant women.
This study shows that the iodine status of pregnant women in Hamilton, New Zealand was inadequate, as indicated by a low UIC (108µg/L) and poor dietary iodine intake (115µg/day). Alternative public health strategies such as the fortification of other staple foods are needed to effectively increase the iodine status of this vulnerable group.