Women Remain at Risk of Iodine Deficiency during Pregnancy: The Importance of Iodine Supplementation before Conception and Throughout Gestation.

In Australia, pregnant women are advised to take an iodine supplement (I-supp) (150 µg/day) to reduce risks to the foetus associated with iodine deficiency (ID). To examine the impact of this recommendation on iodine status, and to identify factors that contribute to adequacy during gestation, supplement use and Urinary Iodine Concentration (UIC) was measured in 255 pregnant women (gestation range 6 to 41 weeks) in Tasmania. The median UIC (MUIC) of 133 µg/L (Inter-quartile range 82⁻233) was indicative of ID, being below the 150⁻249 µg/L range for adequacy during pregnancy. Women taking an iodine-containing-supplement (I-supp) had a significantly higher MUIC (155 µg/L) (n = 171) compared to the combined MUIC (112.5 µg/L) (n = 84) of those who had never (120 µg/L) (n = 61) or were no longer taking an I-supp (90 µg/L) (n = 23) (p = 0.017). Among women reporting I-supp use, the MUIC of those commencing the recommended 150 µg/day prior to conception was significantly higher than those starting supplementation following pregnancy confirmation: 196 (98⁻315) µg/L (n = 45) versus 137.5 (82.5⁻233.5) µg/L (n = 124), p = 0.032. Despite recommendations for iodine supplementation pregnant Tasmanian women remain at risk of ID. Commencing an I-supp of 150 µg/day prior to conception and continuing throughout pregnancy is required to ensure adequacy. Timely advice regarding the importance of adequate iodine nutrition, including supplementation is needed to reduce the risk of irreversible in utero neurocognitive damage to the foetus.

Improved iodine status in Tasmanian schoolchildren after fortification of bread: a recipe for national success.

OBJECTIVES: To examine population iodine status in Tasmania after mandatory iodine fortification of bread and assess the magnitude of difference compared with results from a period of voluntary iodine fortification. DESIGN AND SETTING: A cross-sectional urinary iodine survey of schoolchildren from classes that included fourth-grade students was conducted in Tasmania in 2011. Results were compared with surveys conducted before fortification and during a period of voluntary fortification. PARTICIPANTS: Three hundred and twenty students aged 8-13 2013s from 37 participating school classes. MAIN OUTCOME MEASURES: Median urinary iodine concentration (UIC) and proportion of UIC results < 50 µg/L. RESULTS: Median UIC in 2011 was 129 µg/L, and 3.4% of samples had a UIC under 50µg/L. This was significantly higher than during the period of voluntary fortification (129 µg/L v 108 µg/L) (P> < 0.001), which was significantly higher than before fortification (108 µg/L v 73 µg/L) (P < 0.001). There was a reduction in the proportion of samples with UIC under 50 µg/L after mandatory fortification (3.4%) compared with results from the period of voluntary fortification (9.6%) (P = 0.01), which was a further reduction compared with results from the prefortification period (17.7%) (P < 0.001). CONCLUSIONS: Iodine status in Tasmania can now be considered optimal. Mandatory iodine fortification has achieved significantly greater improvements in population iodine status compared with voluntary fortification. However, surveys of schoolchildren cannot be generalised to pregnant and breastfeeding women, who have higher iodine requirements. Measurement of iodine status in population surveys is warranted for ongoing monitoring and to justify the appropriate level of fortification of the food supply into the future.

A case for universal salt iodisation to correct iodine deficiency in pregnancy: another salutary lesson from Tasmania.

OBJECTIVE: To assess the impact of iodine fortification of bread on the iodine status of pregnant women, and to determine if studies of iodine levels in school-age children were indicative of women's gestational iodine status. DESIGN: Urinary iodine surveys of pregnant Tasmanian women before and after bread was fortified with iodine in October 2001. PARTICIPANTS AND SETTING: 285 women attending the Royal Hobart Hospital (RHH) antenatal clinic from 1 October 2000 to 30 September 2001 and 517 women attending the RHH antenatal clinic or primary health care centres in 2003-2006. MAIN OUTCOME MEASURES: Median urinary iodine concentration (UIC) for comparison against the World Health Organization recommendation of of 150-249 microg/L for pregnant women. RESULTS: Before supplementation, the median UIC of the 285 women attending the RHH antenatal clinic was 76 microg/L. After supplementation, median UICs were 81 microg/L for 288 women attending primary health care centres and 86 microg/L for 229 women attending the RHH antenatal clinic. Differences in mean UIC were not significant for either the antenatal clinic group (P=0.237) or the primary health care group (P=0.809) compared with the pre-supplementation group. CONCLUSIONS: Iodine deficiency in pregnancy persists despite being corrected in Tasmanian children. Successful iodine supplementation must target reproductive-age and pregnant women and be substantiated by ongoing monitoring during pregnancy and lactation. A robust national program for correcting iodine deficiency is urgently needed. Mandatory universal salt iodisation has international endorsement, and should be considered the preferred strategy for eliminating iodine deficiency in Australia.

Iodine status of Tasmanians following voluntary fortification of bread with iodine.

OBJECTIVE: To describe changes in the iodine status of Tasmanians following voluntary fortification of bread with iodine in October 2001. DESIGN AND SETTING: Post-intervention, cross-sectional urinary iodine surveys of Tasmanian schoolchildren aged 8-11 years were used to assess population iodine status. Participants were selected using a one-stage cluster sampling method. The sampling frame comprised classes containing fourth-grade children from all Tasmanian government, Catholic and independent schools. Results were compared with pre-intervention survey results. MAIN OUTCOME MEASURES: Median urinary iodine concentration (UIC) and percentage of UIC < 50 microg/L ascertained from spot urine samples. RESULTS: Median UIC was 75 microg/L in 1998, 72 microg/L in 2000, 105 microg/L in 2003, 109 microg/L in 2004 and 105 microg/L in 2005. Median UIC in post-intervention years (2003-2005) was significantly higher than in pre-intervention years. The percentage of UIC results < 50 microg/L was 16.9% in 1998, 18.7% in 2000, 10.1% in 2003, 10.0% in 2004 and 10.5% in 2005. CONCLUSION: Despite methodological differences between the pre- and post-intervention surveys, switching to iodised salt in bread appears to have resulted in a significant improvement in iodine status in Tasmania. Given iodine deficiency has been identified in other parts of Australia and in New Zealand, mandatory iodine fortification of the food supply in both countries is worthy of consideration. As voluntary fortification relies on industry goodwill, mandating fortification could be expected to enhance population reach and give a greater guarantee of sustainability in Tasmania.