Table 3.

Stratified analysis by the presence of iodine insufficiency and positive thyroid antibodies to test the variations of thyroid hormones from the first to the third trimester in women from the state of Rio de Janeiro, Brazil, September 2014–February 2017

	First trimester		Third trimester
	Mean	sd	Mean	sd	P
Iodine insufficiency*
Yes
TSH (mIU/l)	1·63	1·80	1·69	0·83	<0·001
FT4 (ng/dl)	1·17	0·18	0·87	0·12	<0·001
No
TSH (mIU/l)	1·52	1·13	1·66	0·90	0·001
FT4 (ng/dl)	1·14	0·16	0·89	0·13	<0·001
Positive thyroid antibodies
Yes
TSH (mIU/l)	0·96	0·39	1·54	0·35	0·043
FT4 (ng/dl)	1·11	0·15	0·86	0·20	0·041
No
TSH (mIU/l)	1·41	0·91	1·66	0·88	<0·001
FT4 (ng/dl)	1·19	0·17	0·88	0·12	<0·001

TSH, thyrotropin; FT₄, free thyroxine.

^*Urinary iodine concentration <150 µg/l.