Trimester-Specific Reference Ranges for Thyroid Hormones in Iranian Pregnant Women

Table 2

Gestation specific percentile values for TSH, TT4, and TT3 in a self sequential cohort of 152 pregnant women with normal singleton pregnancies.

	Observed centiles
	5th	50th	95th
TSH (mU/L)
First trimester	0.2	1.5	3.9
Second trimester	0.5	1.8	4.1
Third trimester	0.6	1.8	4.1
TT4 (µg/dL)
First trimester	8.2	12.9	18.5
Second trimester	10.1	14	20.6
Third trimester	9.0	13.4	19.4
TT3 (ng/dL)
First trimester	138	190	278
Second trimester	155	221	328
Third trimester	137	228	324