Table 1.

Reference interval of TSH (mU/L)

	First trimester	Second trimester	Third trimester	Postpartum
Sample size	139	139	139	55
Mean + 2SD
Lower limit	0.37	0.70	0.65	0.58
90% CI	0.26–0.49	0.60–0.80	0.54–0.76	0.47–0.71
Upper limit	3.91	3.97	3.91	3.32
90% CI	3.61–4.22	3.65–4.31	3.61–4.21	2.87–3.84
Percentile non parametric method
Lower limit	0.34	0.68	0.63	0.53
90% CI	0.07–0.55	0.58–0.85	0.32–0.83	–*
Upper limit	3.81	4.07	4.00	3.33
90% CI	3.62–4.81	3.45–4.69	3.51–4.37	–*
Robust method
Lower limit	0.35	0.687	0.631	0.561
90% CI	0.24–0.48	0.560–0.79	0.54–0.74	0.46–0.68
Upper limit	3.95	4.02	3.94	3.42
90% CI	3.63–4.25	3.71–4.33	3.62–4.24	2.92–3.90

–*Not calculated, as recommended by CLSI document EP28-A3c [16]