Iodine during pregnancy

Severe transient postnatal hypothyroidism has been reported in infants whose mothers have received high doses of iodine during pregnancy or multiple local applications of povidone-iodine during pregnancy and for delivery (SED-14, 472). Transient neonatal hypothyroidism during breastfeeding after postnatal maternal topical iodine treatment has also been reported (68). 

Supplementation of iodine during pregnancy is recommended to eliminate iodine-deficiency diseases, especially cretinism in iodine deficiency areas. However, for pregnant women who lived in iodine-excess areas or were exposed to iodine-containing medication during pregnancy, the total iodine intake and their TH status should be closely monitored. 

The findings from animal studies suggest that exposure to excess iodine during pregnancy has an adverse impact on pregnancy and fetal outcome, such as an increased mortality in offspring, an increased incidence of resorptions and especially skeletal variations. 

For the majority of women living in countries with adequate iodine status (i.e., median urinary iodine concentration (MUIC) >150 ig/l), such as Brazil, Canada, the United Kingdom, Japan, and Switzerland (International Atomic Energy Commission, 1992), the additional increment of iodine during pregnancy is likely to be met,... 

Figure 130.1 Extracts of a New Zealand pamphlet designed to raise awareness of the importance of dietary iodine during pregnancy.

Although iodine is an essential nutrient that is required for proper prenatal development, infants are reported to be particularly sensitive to the effects of iodine (Baker 2004), and cases of infanf goiter after maternal use of iodine during pregnancy or lactation have been reported (Pennington 1990). Also see Editors Notes for this entry. 

RECOMMENDED DIETARY ALLOWANCE OF IODINE DURING PREGNANCY... 

WHO/UNICEF/ICCIDD. Iodized oil during pregnancy. Safe use of iodized oil to prevent iodine deficiency in pregnant women. Geneva (Switzerland) World Health Organization 1996. (WHO/NUT/96.5). 

Delange F Iodine requirements during pregnancy, lactation and the neonatal period and indicators of optimal iodine nutrition. Public Health Nutr 2007 10 1571. [PMID 18053281]... 

Neonatal goiter caused by the use of potassium iodine as an expectorant during pregnancy has been reported (67). The neonate, a girl, had acute hypothyroidism, with myxedema and respiratory distress. She was given levothyroxine for 6 months, with complete normalization of thyroid function. 

Skin disinfection with iodine also caused goiter and hypothyroidism in five of 30 newborns under intensive care (69). Antiseptics containing iodine should be avoided not only during pregnancy and delivery but also after the delivery during breastfeeding. 

Goh KO. Radioiodine treatment during pregnancy chromosomal aberrations and cretinism associated with maternal iodine-131 treatment. J Am Med Womens Assoc 1981 36(8) 262-5. 

Mahillon I, Peers W, Bourdoux P, Ermans AM, Delange F. Effect of vaginal douching with povidone-iodine during early pregnancy on the iodine supply to mother and fetus. Biol Neonate 1989 56(4) 210-7. 

Other treatment options, besides thioamide therapy, involve RAI. The iodine 131 isotope is taken up by the thyroid gland and the radioactivity destroys the gland. RAI is safe, pain free, easy to administer, and very effective. RAI may result in euthyroidism but more frequently results in hypothyroidism requiring lifelong levothyroxine supplementation. RAI should never be given during pregnancy since it crosses the placenta. 

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