Background: Periodontitis is considered to be a risk factor for preterm birth. Mechanisms have been proposed for this pathologic relation, but the exact pathologic pattern remains unclear. Therefore, the objective of the present study is to evaluate levels of four major labor triggers, prostaglandin E 2 (PGE[2]), interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, in gingival crevicular fluid (GCF) and serum samples between women with preterm birth (PTB) and full-term birth (FTB) and correlate them with periodontal parameters. Methods: PGE[2] , IL-1β, IL-6, and TNF-α levels were estimated using enzyme-linked immunosorbent assays in GCF and serum samples collected 24 to 48 hours after labor from 120 women (60 FTB, 60 PTB). Results: Women with PTB exhibited significantly more periodontitis, worse periodontal parameters, and increased GCF levels of IL-6 and PGE 2 compared with the FTB group; there were no significant differences in serum levels of measured markers. GCF levels of IL-1β, IL-6, and PGE[2] and serum levels of TNF-α and PGE[2] were significantly higher in women with periodontitis compared with periodontally healthy women. Serum levels of PGE[2] were positively correlated with probing depth (PD) and clinical attachment level (CAL) as well as with GCF levels of TNF-a in women with PTB. Conclusions: Women with PTB demonstrated worse peri-odontal parameters and significantly increased GCF levels of IL-6 and PGE[2] compared with those with FTB. Based on significant correlations among serum PGE[2] and PD, CAL, and GCF TNF-α in PTB, periodontitis may cause an overall increase of labor triggers and hence contribute to preterm labor onset.