Intra-amniotic administration of lipopolysaccharide induces spontaneous preterm labor and birth in the absence of a body temperature change

Objective: Intra-amniotic infection is associated with spontaneous preterm labor. In most cases, the infection is subclinical and bacteria are detected in the amniotic cavity rather than in the chorioamniotic membranes. The aims of this study were to establish a model of intra-amniotic lipopolysaccharide (LPS)-induced preterm labor/birth that resembles the subclinical syndrome and to compare this model to two established models of LPS-induced preterm labor/birth.Methods: Pregnant B6 mice received an intra-amniotic, intra-uterine, or intra-peritoneal injection of LPS (100ng/amniotic sac, 15g/25L, and 15g/200L respectively) or PBS (control). Following injection, body temperature (every two hours for a 12-h period), gestational age, and the rate of preterm labor/birth were recorded.Results: An intra-amniotic injection of LPS resulted in preterm labor/birth [LPS 8024.79% (8/10) versus PBS 0% (0/8); p=0.001] without causing maternal hypothermia. Intra-peritoneal [LPS 100% (8/8) versus PBS 0% (0/8); p<0.001)] and intra-uterine [LPS 100% (8/8) versus PBS 28.57 +/- 33.47% (2/7); p=0.007] injections of LPS induced preterm labor/birth; yet, maternal hypothermia was observed.Conclusion: Intra-amniotic injection of LPS induces preterm labor/birth in the absence of a body temperature change, which resembles the subclinical syndrome.