Table 2.

Summary of meta-analyzes regarding intervention trials with iodine supplementation in pregnant women

Author	Evaluation of iodine supplementation	N. included trials	Maternal/Neonatal Outcomes		Results
Harding et al.[27]	injected or oral iodine supplementation during preconception, pregnancy (PR) and postpartum (PP) vs. placebo/no treatment	1 (PR) -3 (PP)	maternal primary outcomes	Hypothyroidism (in pregnancy/post partum)	no difference
		2		Preterm birth	no difference
		1 (PR) -3 (PP)		Elevated TPOAb	no difference
		1 (PR) -3 (PP)		Hyperthyroidism (in pregnancy/post partum)	68% reduction in postpartum hyperthyroidism, no differences in pregnancy
		1		Digestive intolerance	digestive intolerance increased 15 times compared to placebo
		1	infant primary outcomes	Perinatal mortality	trend lower perinatal mortality, not significant
		2		Low birthweight (< 2500 g)	no difference
		1		Neonatal hypothyroidism or elevated TSH	No difference
		1		Neonatal adverse effect: elevated TPOAb	no difference
Dineva et al.[28]	Supplementation vs. no supplementation in mildly-to-moderately deficient women (UIC: 50–149 µg/L)	2	maternal thyroid function (TSH; FT4) during pregnancy (second and third trimester)		Lower TSH in second and third trimester in treated women. Lower FT4 only in third trimester in treated women.
		2	Children neurodevelopment (Bayley scores)		no effect of iodine supplementation compared with placebo on child cognitive, language, or motor scores.
Nazeri et al.[26]	Any supplementation vs. no supplementation during pregnancy	5	Newborn weight		No difference
		3	Newborn length		No difference
		2	Newborn Head circumference		No difference
		3	Cognitive development		No difference
		3	Language development		No difference
		3	Motor development		No difference

Abbreviations: TPO Ab – Anti-Thyroperoxidase Antibodies; TSH -Thyroid-Stimulating Hormone; UIC -Urinary Iodine Concentration, FT4 - Free-thyroxine