Preterm labor is a delivery of the fetus before completed thirty seven weeks of gestation .It is associated with considerable perinatal morbidity and mortality.Many factors contribute to the etiology of preterm labor including microbial and non-microbial factors.Bacterial infections especially Gram negative bacteria are the main trigeres for the preterm labor.Host immune response against bacterial infections mediated by cytokines mainly tumor necrosis -alpha play an important role in inflammatory reactions associated with preterm labor.This work hilights on the identification and characterization of bacteria isolated from pregnant with preterm labor, detection of bacterial virulence factors and study the immune parameters of humoral and cellular response in the pregnant with preterm labor