Pregnancy Loss and Iodine Status: The LIFE Prospective Cohort Study.

James Mills,Yanjian Wan,Joe Maisog,Kurunthachalam Kannan,Andreas Giannakou,Ali Mehnaz,Rajeshwari Sundaram,Germaine Buck Louis,Jennifer Weck

doi:10.3390/nu11030534

Abstract

Iodine deficiency in pregnancy is a common problem in the United States and parts of Europe, but whether iodine deficiency is associated with increased pregnancy loss has not been well studied. The LIFE study provided an excellent opportunity to examine the relationship between iodine status and pregnancy loss because women were monitored prospectively to ensure excellent ascertainment of conceptions. The LIFE study, a population-based prospective cohort study, monitored 501 women who had discontinued contraception within two months to become pregnant; 329 became pregnant, had urinary iodine concentrations measured on samples collected at enrollment, and were followed up to determine pregnancy outcomes. Of the 329, 196 had live births (59.5%), 92 (28.0%) had losses, and 41 (12.5%) withdrew or were lost to follow up. Urinary iodine concentrations were in the deficiency range in 59.6% of the participants. The risk of loss, however, was not elevated in the mildly deficient group (hazard ratio 0.69, 95% confidence interval 0.34, 1.38), the moderately deficient group (hazard ratio 0.81, 95% confidence interval 0.43, 1.51), or the severely deficient group (hazard ratio 0.69, 95% confidence interval 0.32, 1.50). Iodine deficiency, even when moderate to severe, was not associated with increased rates of pregnancy loss. This study provides some reassurance that iodine deficiency at levels seen in many developed countries does not increase the risk of pregnancy loss.

Highlights

Inadequate maternal iodine stores during pregnancy result in insufficient thyroid hormone production with serious adverse effects in the offspring
(referent: underweight/normal), time-to-pregnancy, creatinine, average daily smoking in periconception window, average daily alcohol consumption in periconception window, diabetes and previous losses, history of hypothyroidism, history of hyperthyroidism. c Adjusted models: same as above except for history of hypothyroidism, history of hyperthyroidism. d Adjusted models: Same as above except for creatinine. In this first prospective cohort study, women in the iodine deficient groups did not experience a significantly increased rate of losses compared to the group whose samples were in the iodine sufficient range
This is reassuring because of the 329 iodine measurements available, 21.3% were in the severe deficiency range, 22.5% were in the moderate deficiency range and an additional 15.8%

Summary

Introduction

Inadequate maternal iodine stores during pregnancy result in insufficient thyroid hormone production with serious adverse effects in the offspring. Thyroid deficiency has been reported to increase the risk for pregnancy loss as well as abnormal fetal development; whether iodine status is related to fetal loss is less clear [2]. This is an important problem because US pregnant women had a median urinary iodine concentration of. In Europe, urinary iodine excretion in pregnant women in eight iodine deficient countries was between 35 and 150 μg/L, most well below the range defined by the WHO as sufficient [5]

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Results

Conclusion