Table 2.

Baseline characteristics of analyzable subjects (n=204), according to results of PCR and culture of amniotic fluid.

Characteristic	Negative culture and negative PCR (n=103)	P*	Negative culture but positive PCR (n=31)	P†	Positive culture (n=70)	Missing Culture Data (n=26)
Maternal age (y, mean ± SD)	29.4 ± 7.3	0.2	27.5 ± 8.0	0.6	28.4 ± 7.6	28.9 ± 7.1
Nulliparity (N=55)	19/103 (19%)	<0.05	12/31 (39%)	0.2	18/70 (26%)	6/26 (23%)
Cervical insufficiency (N=6)	1/103 (1%)	0.1	2/31 (7%)	0.6	3/70 (4%)	0/26 (0%)
Smoking (N=44)	18/103 (18%)	0.6	7/31 (23%)	0.2	8/70 (11%)	11/26 (42%)
Alcohol use (N=14)	7/103 (7%)	0.7	1/31 (3%)	1	2/70 (3%)	4/26 (15%)
Drug use (N=2)	2/103 (2%)	1	0/31 (0%)	NA	0/70 (0%)	0/26 (0%)

^*Comparison of a negative culture and negative PCR with a negative culture but positive PCR.

^†Comparison of a negative culture but positive PCR with a positive culture.

P values for comparison of mean maternal age were calculated using Student’s t-test, and assumed unequal variances.

P values for proportions were calculated using Fisher’s exact test.