Maternal thyroid dysfunction during gestation, preterm delivery, and birthweight. The Infancia y Medio Ambiente Cohort, Spain.

BACKGROUND: Maternal clinical thyroid disorders can cause reproductive complications. However, the effects of mild thyroid dysfunctions are not yet well established. The aim was to evaluate the association of maternal thyroid function during the first half of pregnancy with birthweight and preterm delivery. METHODS: We analysed data on 2170 pregnant women and their children from a prospective population-based cohort study in four Spanish areas. Mid-gestation maternal serum and urine samples were gathered to determine thyroid-stimulating hormone (TSH), free thyroxine (fT4 ), and urinary iodine concentration (UIC). Thyroid status was defined according to percentile distribution as: euthyroid (TSH and fT4 >5th and <95th percentiles); hypothyroxinaemia (fT4 < 5 th percentile and TSH normal), hypothyroidism (TSH > 95th percentile and fT4 normal or <5th percentile), hyperthyroxinaemia (fT4 > 95 th percentile and TSH normal), and hyperthyroidism (TSH < 5 th percentile and fT4 normal or >95th percentile). Response variables were birthweight, small and large for gestational age (SGA/LGA), and preterm delivery. RESULTS: An inverse association of fT4 and TSH with birthweight was found, the former remaining when restricted to euthyroid women. High fT4 levels were also associated with an increased risk of SGA [odds ratio, 95% confidence interval (CI) 1.28 (95% CI 1.08, 1.51)]. Mean birthweight was higher in the hypothyroxinaemic group (ß = 109, P < 0.01). Iodine intake and UIC were not associated with birth outcomes. CONCLUSIONS: High maternal fT4 levels during the first half of pregnancy were related to lower birthweight and increased risk of SGA newborns, suggesting that maternal thyroid function may affect fetal growth, even within the normal range.

Trends in children's exposure to second-hand smoke in the INMA-Granada cohort: an evaluation of the Spanish anti-smoking law.

The smoke-free legislation implemented in Spain in 2006 imposed a partial ban on smoking in public and work places, but the result did not meet expectations. Therefore, a more restrictive anti-smoking law was passed five years later in 2011 prohibiting smoking in all public places, on public transport, and the workplace. With the objective of assessing the impact of the latter anti-smoking legislation on children's exposure to second-hand smoke (SHS), we assessed parent's smoking habits and children's urine cotinine (UC) concentrations in 118 boys before (2005-2006) and after (2011-2012) the introduction of this law. Repeated cross-sectional follow-ups of the "Environment and Childhood Research Network" (INMA-Granada), a Spanish population-based birth cohort study, at 4-5 years old (2005-2006) and 10-11 years old (2011-2012), were designed. Data were gathered by ad-hoc questionnaire, and median UC levels recorded as an objective indicator of overall SHS exposure. Multivariable logistic regression was used to examine the association between parent's smoking habits at home and SHS exposure, among other potential predictors. An increase was observed in the prevalence of families with at least one smoker (39.0% vs. 50.8%) and in the prevalence of smoking mothers (20.3% vs. 29.7%) and fathers (33.9% vs. 39.0%). Median UC concentration was 8.0ng/mL (interquartile range [IQR]: 2.0-21.8) before legislation onset and 8.7ng/mL (IQR: 2.0-24.3) afterwards. In the multivariable analysis, the smoking status of parents and smoking habits at home were statistically associated with the risk of SHS exposure and with UC concentrations in children. These findings indicate that the recent prohibition of smoking in enclosed public and workplaces in Spain has not been accompanied by a decline in the exposure to SHS among children, who continue to be adversely affected. There is a need to target smoking at home in order to avoid future adverse health effects in a population that has no choice in the acceptance or not of SHS exposure-derived risk.