Table 2.

Distributions of characteristics and RTL between GDM cases and controls.

Variables	Cases	RTL Mean ± SD	Controls	RTL Mean ± SD	P a
	N (%)		N (%)
Overall	113		396
Maternal age at delivery (years)
<25	15 (13.27)	0.360 ± 0.163	62 (15.66)	0.355 ± 0.208	0.940
25~30	51 (45.13)	0.227 ± 0.082	212 (53.54)	0.338 ± 0.165	0.014
30~35	32 (28.32)	0.297 ± 0.071	97 (24.49)	0.315 ± 0.132	0.482
≥35	15 (13.27)	0.341 ± 0.176	25 (6.31)	0.352 ± 0.137	0.829
BMI (kg/m 2 )
<25%	23 (20.35)	0.326 ± 0.147	98 (24.75)	0.338 ± 0.161	0.759
25%~50%	28 (24.78)	0.290 ± 0.078	100 (25.25)	0.337 ± 0.213	0.089
50%~75%	22 (19.47)	0.321 ± 0.105	99 (25.00)	0.345 ± 0.156	0.512
≥75%	40 (35.40)	0.285 ± 0.114	99 (25.00)	0.324 ± 0.111	0.081
Maternal exposure to secondhand smoke
≥Half an hour a day	9 (7.96)	0.283 ± 0.075	27 (6.28)	0.367 ± 0.210	0.257
<Half an hour a day	21 (18.59)	0.293 ± 0.099	101 (25.51)	0.361 ± 0.222	0.173
Never	83 (73.45)	0.307 ± 0.121	268 (67.67)	0.326 ± 0.132	0.289
Pregnant experience
Ever	51 (45.13)	0.315 ± 0.129	167 (42.17)	0.335 ± 0.152	0.422
Never	62 (54.87)	0.291 ± 0.095	229 (57.83)	0.337 ± 0.172	0.054
Regular exercises
Daily	6 (5.31)	0.307 ± 0.093	17 (4.29)	0.258 ± 0.138	0.431
3~6 Times per week	3 (2.65)	0.238 ± 0.047	27 (6.82)	0.307 ± 0.127	0.366
1~2 Times per week	28 (24.78)	0.312 ± 0.091	109 (27.53)	0.307 ± 0.124	0.874
Never	76 (67.26)	0.300 ± 0.123	243 (61.36)	0.358 ± 0.181	0.013

^aDerived from t-test for RTL between cases and controls.