A Nested Case-Control Study of the Relationship between Salivary Inflammatory Mediators, Periodontal Parameters, and Preterm Birth in a Chinese Population

Table 1

Demographic characteristics at enrollment in FTB and PTB group.

Demographic variable	FTB ()	PTB ()	value
Mean age (years)			0.10
Gestation weeks (weeks)			0.93
BMI (kg/m^2)			0.53
Prior deliveries	94 (30.1%)	8 (32.0%)	0.85
Occupation	266 (85.3%)	13 (50.0%)	<0.01
Education			0.72
≤High school	53 (17.0%)	3 (11.5%)
≥College	259 (83.0%)	23 (88.5%)
Ethnicity			0.43
Han	304 (97.4%)	26 (100%)
Minority	8 (2.6%)	0 (0%)
Health insurance	307 (98.4%)	26 (100%)	1.00
Alcohol	16 (5.2%)	3 (11.5%)	0.16
Brushing times			0.02
Once a day	20 (6.4%)	5 (19.2%)
Twice a day or more	292 (93.6%)	21 (80.8%)
Brushing time			1.00
No more than 3 minutes	279 (89.4%)	23 (88.5%)
More than 3 minutes	33 (10.6%)	3 (11.5%)
Dental floss	89 (28.5%)	7 (26.9%)	0.96
Supragingival scaling history	147 (47.1%)	12 (46.2%)	0.88
Bleeding gum before pregnancy	167 (53.5%)	11 (42.3%)	0.37
Bleeding gum during pregnancy	177 (56.7%)	15 (57.7%)	0.76

. FTB: full term birth; PTB: preterm birth.