HEALTH NEWS

Study Title:

Iodine and Prenatal Growth

Study Abstract

Introduction: The fetus is the most vulnerable to severe iodine deficiency and hypothyroidism during pregnancy. The effects of mild iodine deficiency and subclinical hypothyroidism are poorly known. The present study assesses the association between thyroid hormones and urinary iodine concentration (UIC) in healthy pregnant women and the birth weight of their children.

Methods: 657 pregnant women were recruited in Sabadell and followed until delivery. The association between thyroid hormones during the first trimester, UIC during the first and third trimesters and birth weight was studied in 557, 251 and 528 mother-newborn pairs, respectively, using linear and logistic regression models adjusted for potential confounders. Only 239 women had all data available (thyroid function and UIC at first and at third trimesters). Six percent of newborns were classified as SGA.

Results: The median UIC was 95mug/L and 104mug/L during the first and third trimesters, respectively. Women with third trimester UICs between 100mug/L and 149mug/L had lower risk of having a SGA newborn than women with UICs below 50mug/L (adjusted OR (95%CI): 0.15 (0.03-0.76). There was no significant reduction in SGA among mothers with higher UICs. Lower free T4 and higher TSH levels during the first trimester were not associated with birth weight or SGA. Nevertheless, analysis were repeated including only those women with all data available, and high TSH levels become statistically significantly associated with lower birth weight and higher risk of SGA.

Conclusions: The present study suggests that iodine status during pregnancy may be related to prenatal growth in healthy women.

Study Information

Alvarez-Pedrerol M, Guxens M, Mendez M, Canet Y, Martorell R, Espada M, Plana E, Rebagliato M, Sunyer J.
Iodine levels and thyroid hormones in healthy pregnant women and birth weight of their offspring.
Eur J Endocrinol.
2008 December
Centre for Research in Environmental Epidemiology, Barcelona, 08003, Spain.