Objective To evaluate the associations between periodontal conditions, serum level of interleukin- 1β （IL- 1β） and delivery outcomes in pregnant women with a diagnosis of threatened premature labor（TPL）. Methods Eighty systemically healthy pregnant women were enrolled in the study. The case group was composed of 40 pregnant women hospitalized with the diagnosis of TPL（TPL group） and the control group was composed of 40 normal pregnant women（Non - TPL group）. eriodontal examinations included assessments of plaque index（PLI）, clinical attachment loss（CAL）, probing depth（PD）, bleeding index（BI） and the percent of periodontitis sites（PD>3 mm, CAL≥2 mm）. The serum level of IL- 1βwas determined using commercially available enzyme- linked immunoassays. Results ①Fourteen of forty subjects of TPL group delivered premature labor infants（TPL- TB group）, and twentysix subjects delivered natural labor infants（TPL- PB group）. No infants were delivered as premature labor infants in non- TPL group. There were significant differences in gestational age at delivery, birth weight, PLI, percentage of periodontitis sites and IL- 1β levels between the non- TPL group and TPL group or between the TPL- TB group and TPL- PB group（P
