Table 1.

Subject characteristics in the TPL group and H group

	TPL group (n = 47)	H group (n = 48)	P-value
Demographic characteristics
Age (years)	33.5 ± 4.8	32.8 ± 3.9	NS
Smoking history (%)	29.8 (14/47)	20.8 (10/48)	NS
Periodontal parameters
Mean PPD (mm)	2.34	2.3	NS
CAL (mm)	2.4	2.4	NS
Sites with a PPD of ≥ 5 mm (%)	0	0	NS
BOP (%)	20.7	22.2	NS
Laboratory values
Porphyromonas gingivalis. in the plaque (16s rDNA copies)	1.29	0	NS
Porphyromonas gingivalis. (+)% in the plaque	51.0 (24/47)	43.7 (21/48)	NS
Porphyromonas gingivalis. in the saliva (16s rDNA copies)	43.6	204	NS
Porphyromonas gingivalis. (+)% in the saliva	53.2 (25/47)	60.4 (29/48)	NS
Titre of anti-Porphyromonas gingivalis. IgG	7.1	6.5	NS
Concentration of anti-Porphyromonas gingivalis. IgG1	17.2*	23.5	0.04
Concentration of anti-Porphyromonas gingivalis. IgG2	2.7	2.8	NS
Concentration of anti-Porphyromonas gingivalis. IgG3	3.2	3.3	NS
Concentration of anti-Porphyromonas gingivalis. IgG4	0.4	0.5	NS
Serum hs-CRP (ng/mL)	1048	1326	NS
Pregnancy outcomes
PB rate	27.7 (13/47)*	2.1 (1/48)	0.0004
LBW rate	29.8 (14/47)*	6.25 (3/48)	0.003
SGA rate (%)	29.8 (14/47)*	6.25 (3/48)	0.003
Birth week	37.9 ± 2.2*	39.4 ± 2.8	0.0003
Birth weight (g)	2914.7 ± 490.1*	3107.6 ± 419.1	0.0438
Placenta weight (g)	617.0 ± 136.8	596.7 ± 113.4	NS

Parametric continuous variables were tested using an unpaired t-test and are given as means ± standard deviations; non-parametric continuous variables were tested using the Mann–Whitney U-test and are given as medians.

BOP, bleeding on probing; CAL, clinical attachment loss; H, healthy; hs-CRP, high-sensitivity C-reactive protein; Ig, immunoglobulin; LBW, low birth weight; NS, not significant; PB, preterm birth; PPD, pocket probing depth; SGA, small for gestational age; TPL, threatened preterm labour.

^*Significantly different from the H group (P < 0.05).