. 2013 May 15;29(2):167–173. doi: 10.1007/s12291-013-0332-1

Table 1.

Descriptive statistics of reference population partitioned into three trimesters

Trimester	Parameter	Distribution	Mean ± SD	Median	2.5 Percentile	97.5 Percentile
First trimester (N = 125)	TSH (μIU/ml)	Normal (Parametric estimation)	1.81 ± 0.79	1.8	0.25	3.35
First trimester (N = 125)	fT₄ (ng/dl)	Not normal (Nonparametric rank based estimation)	1.36 ± 0.35	1.4	0.64	2.0
Second trimester (N = 151)	TSH (μIU/ml)	Not normal (Nonparametric rank based estimation)	2.22 ± 1.10	1.84	0.78	4.96
Second trimester (N = 151)	fT₄ (ng/dl)	Not normal (Nonparametric rank based estimation)	1.27 ± 0.38	1.28	0.53	2.02
Third trimester (N = 126)	TSH (μIU/ml)	Not normal (Ln transformed parametric estimation)	2.2 ± 0.88	2.07	0.9	4.6
Third trimester (N = 126)	fT₄ (ng/dl)	Normal (Parametric estimation)	1.31 ± 0.34	1.33	0.64	1.99