Maternal Iodine Status and Associations with Birth Outcomes in Three Major Cities in the United Kingdom

Abstract

Severe iodine deficiency in mothers is known to impair foetal development. Pregnant women in the UK may be iodine insufficient, but recent assessments of iodine status are limited. This study assessed maternal urinary iodine concentrations (UIC) and birth outcomes in three UK cities. Spot urines were collected from 541 women in London, Manchester and Leeds from 2004–2008 as part of the Screening for Pregnancy End points (SCOPE) study. UIC at 15 and 20 weeks’ gestation was estimated using inductively coupled plasma-mass spectrometry (ICP-MS). Associations were estimated between iodine status (UIC and iodine-to-creatinine ratio) and birth weight, birth weight centile (primary outcome), small for gestational age (SGA) and spontaneous preterm birth. Median UIC was highest in Manchester (139 μg/L, 95% confidence intervals (CI): 126, 158) and London (130 μg/L, 95% CI: 114, 177) and lowest in Leeds (116 μg/L, 95% CI: 99, 135), but the proportion with UIC <50 µg/L was <20% in all three cities. No evidence of an association was observed between UIC and birth weight centile (−0.2% per 50 μg/L increase in UIC, 95% CI: −1.3, 0.8), nor with odds of spontaneous preterm birth (odds ratio = 1.00, 95% CI: 0.84, 1.20). Given the finding of iodine concentrations being insufficient according to World Health Organization (WHO) guidelines amongst pregnant women across all three cities, further studies may be needed to explore implications for maternal thyroid function and longer-term child health outcomes.

Maternal and neonatal outcomes and determinants of iodine deficiency in third trimester of pregnancy in an iodine sufficient area

“…Using a multivariate logistic regression in this study showed that neonate of mothers with urinary iodine levels below 150 micrograms/litre were 4.6 times more hospitalised in NICU and preterm outcome for the neonates of mothers with UIC below 150 micrograms/litre were 3.3 times more frequent in comparison with referent group. In a recent study in three major cities across the UK, researchers found no relation between iodine deficiency and low birth weight and preterm labour [40]. Walsh et al did not find any relation between maternal low iodine intake and perinatal mortality and neural development of the neonates of these mothers [41].…”

Iodine Status, Thyroid Function, and Birthweight: A Complex Relationship in High-Risk Pregnancies

“…On the other hand, nutritional intake during pregnancy is particularly critical for directing normal fetal growth and development [35], so the influence of maternal iodine status on birth weight has been extensively studied. However, while some studies have demonstrated that babies born to women with inadequate dietary iodine intake in the third trimester had lower birth weights than those born to women with adequate intake [36,37], most of them showed no evidence of an association between UIC and birth weight [38][39][40]. This mismatch is based on a great heterogeneity among studies due to a different degree of iodine deficiency (severe vs. moderate-to-mild deficiency); different timing (first trimester, half-gestation, at birth), and different methodology in the evaluation [12,14].…”

Iodine Levels in Pregnant Women with Hyperemesis Gravidarum

“…In the literature, the relationship between iodine levels and pregnancy complications have been evaluated in several studies (15)(16)(17). Porterfield et al have suggested that iodine has a crucial role in the development of thyroid hormone, which also contributes to the neurological development of fetuses.…”