Table 1.

Reference intervals for TSH and FT4 in each trimester of pregnancy and in nonpregnant women.

Groups	N	TSH (mIU/L)			FT4 (pmol/L)
		Median	2.5th percentile	97.5th percentile	Median	2.5th percentile	97.5th percentile
Nonpregnant	237	2.69	0.69	5.78	11.60	8.24	16.61
Pregnancy
First trimester	398	1.30	0.07	3.96	13.10	9.16	18.12
Second trimester	797	1.64	0.27	4.53	11.70	8.67	16.21
Third trimester	1345	2.10	0.48	5.40	10.30	7.80	13.90