Relative impact of iodine supplementation and maternal smoking on cord blood thyroglobulin in pregnant women with normal thyroid function.
OBJECTIVE
To assess the impact on cord blood (CB) thyroglobulin (Tg) of early iodine supplementation during pregnancy.


METHODS
A total of 111 healthy pregnant women with normal thyroid function were included in a prospective randomized study and divided into two groups with (150 μg/day) or without iodine supplementation started during the first trimester. Maternal smoking was assessed qualitatively by self-reported statements and quantitatively by cotininuria. Exhaustive thyroid tests were performed at delivery in the mother and in CB.


RESULTS
Third-trimester ioduria documented compliance with iodine supplementation (160 vs. 76 μg/l in controls). CB Tg was not different between the iodine and control groups (median 77 vs. 79.5 ng/ml, respectively) and did not correlate with maternal ioduria. CB Tg was higher in newborns from smoking mothers (114 vs. 64.7 ng/ml) and correlated with self-reported smoking status more than with maternal cotininuria. Nonsmokers had no difference in CB Tg whether they took iodine supplementation or not, as opposed to smokers, who tended to benefit from supplementation.


CONCLUSIONS
Iodine supplementation does not significantly impact CB Tg in healthy nonsmoker pregnant women selected for normal thyroid function, as opposed to maternal smoking. CB Tg appears to be a marker of in utero tobacco exposure. In areas of mild iodine deficiency, iodine supplementation could especially benefit the fetuses of smokers.
Department of Endocrinology, Diabetology and Reproductive Medicine, University Hospital of Nice, Nice, France.
Sylvie
S
Hiéronimus
Department of Biochemistry, University Hospital of Nice, Nice, France.
Patricia
P
Ferrari
Department of Biostatistics, University of Nice, Nice, France.
Jocelyn
J
Gal
Department of Biostatistics, University of Nice, Nice, France.
Frédéric
F
Berthier
Institute of Chemistry, UMR 6001, University of Nice-Sophia-Antipolis, Nice, France.
Stéphane
S
Azoulay
Department of Gynaecology and Obstetrics, University Hospital of Nice, Nice, France.
André
A
Bongain
Department of Endocrinology, Diabetology and Reproductive Medicine, University Hospital of Nice, Nice, France ; Institut National de la Recherche Médicale, UMR U895, University Nice-Sophia-Antipolis, Nice, France.
Patrick
P
Fénichel
Department of Endocrinology, Diabetology and Reproductive Medicine, University Hospital of Nice, Nice, France ; Institut National de la Recherche Médicale, UMR U895, University Nice-Sophia-Antipolis, Nice, France.
Françoise
F
Brucker-Davis
Cord blood; Iodine; Pregnancy; Smoking; Thyroglobulin; Thyroid tests