Table 2. Comparisons of the clinical data from four groups of pregnant women with different FT4 trends during pregnancy.

Characteristics	Normal/normal	Low/low	Low/normal	Normal/low
	n = 4672	n = 228	n = 608	n = 523
Age (year)	29.9±3.1	30.8±3.2 **	31.0±3.3 **	30.2±3.1
BMI (kg/m2)	21.83±2.80	23.59±2.95 **	23.48±5.66 **	22.25±2.75 **
Gestational weeks (at Delivery)	38.9±1.7	39.0±1.2	38.9±1.6	39.0±1.5
TSH (mIU/L)
First Trimester	1.16±0.64	1.37±0.58 **	1.33±0.61 **	1.21±0.66
Third Trimester	1.53±0.67	1.61±0.65	1.59±0.66	1.61±0.67 *
FT4 (pmol/L)
First Trimester	15.45±1.18	12.61±0.65 **	12.84±0.54 **	15.02±1.11
Third Trimester	12.11±0.98	9.60±0.59 **	11.65±0.85	9.81±0.45 **

BMI: Body mass index; TSH: Thyroid-stimulating hormone;

*P<0.05,

**P<0.01, compared with Normal/normal group.