TABLE 2.

Covariate-adjusted associations between urinary iodine levels and plasma thyroglobulin, prenatal multivitamin use, and prepregnancy body mass index

Categorical urinary iodinea	Plasma Tgb,c			Prenatal multivitamind			Prepregnancy BMIe
	N	B	95% CI	N	aOR	95% CI	n	B	95% CI
UIC (μg/L)
<150	509	−0.018	−0.10 to 0.07	554	0.63f	0.46–0.89f	555	−0.15	−0.73 to 0.43
150–499	466	Ref		762	Ref		762	Ref
≥500	82	−0.048	−0.21 to 0.11	82	1.88	0.74–4.78	82	1.19	−0.03 to 2.41
UIC/Cr (μg/g)
<150	221	0.15f	0.05–0.26f	151	0.36f	0.24–0.54f	151	1.38f	0.47–2.29f
150–499	638	Ref		1006	Ref		1007	Ref
≥500	197	0.013	−0.10 to 0.12	230	2.70f	1.43–5.12f	230	−2.01f	−2.77 to −1.26f

aOR, adjusted odds ratio; B, unstandardized Beta coefficient; BMI, body mass index; CI, confidence interval; Tg, thyroglobulin; UIC, urinary Iodine concentration; UIC/Cr, urinary iodine concentration adjusted for creatinine.

^a<150 μg/L (μg/g)=low iodine range; 150–499 μg/L (μg/g)=mid iodine range; ≥500 μg/L (μg/g)=high iodine range;

^bAssociations between UIC or UIC/Cr with natural log-transformed Tg were examined using trimester 1 data;

^cAssociations adjusted for maternal age, prepregnancy BMI, trimester 1 smoking, and ethnicity (defined as White vs non-White). Women who were Tg antibody (Ab)- and/or thyroid peroxidase Ab-positive (n=342) and had a known thyroid condition (n=69) were removed from the analyses;

^dAssociations adjusted for maternal age, prepregnancy BMI, trimester 1 smoking, and ethnicity, excluding women with a known thyroid condition;

^eAssociations adjusted for maternal age, trimester 1 smoking, and ethnicity, excluding women with a known thyroid condition;

^fSignificant associations (P<.05).