Table 2.

Comparison of Serum Thyrotropin and Thyroid Hormone Concentrations Among Euthyroid Mothers (With or Without Thyroid Autoantibodies) of Different Smoking Status

Smoking status	n	TSH (mU/L)	fT4 (pmol/L)	fT3 (pmol/L)
Smoking before pregnancy
Smokers	1335	1.06	15.02	5.26
Nonsmokers	3305	1.03	15.17	5.05
p-Value		NS	0.019	<0.001
Smoking in the first trimester
Smokers	806	1.02	15.02	5.27
Nonsmokers	3511	1.02	15.24	5.07
p-Value		NS	0.006	<0.001
Smoking in the second trimester
Smokers	108	1.20	14.53	5.48
Nonsmokers	316	1.27	14.38	5.10
p-Value		NS	NS	<0.001
Quit smoking before serum sampling
Quit smoking	298	1.14	14.92	5.19
Nonsmokers	3288	1.03	15.18	5.05
p-Value		0.008	0.037	0.005
Quit smoking or continued smoking in early pregnancy
Quit smoking	298	1.14	14.93	5.19
Continued smoking	459	1.07	14.96	5.22
p-Value		NS	NS	NS
Only husband smokes
Smokers	822	1.05	15.16	5.07
Nonsmokers	2131	1.02	15.17	5.04
p-Value		NS	NS	NS
Both smoke
Smokers	805	1.06	15.00	5.21
Nonsmokers	3305	1.04	15.17	5.05
p-Value		NS	0.012	<0.001

Figures are geometric means. A p-value <0.05 was deemed significant.

TSH, thyrotropin; fT3, free triiodothyronine; fT4, free thyroxine; NS, nonsignificant.