U-M are common commensal of the urogenital tract of sexually mature humans, are gaining recognition as an important opportunistic pathogen during pregnancy. Furthermore, ureaplasmal and mycoplasmal infection of the chorioamnion is significantly associated with premature spontaneous labor and delivery. Although risk factors for colonization of the lower genitourinary tract have been identified, little information is available concerning risk factors for intrauterine infection and host immune responses to invasive infection. However, the most critical need is additional information concerning indications for diagnosis and treatment as well as efficacy of treatment. Material and methods 263 asymptomatic pregnant women between 24 and 34 weeks of gestation were examined in our clinic in Tirana. All these women were tested for the presence of ureaplasma and mycoplasma by vaginal smear. Results The study found that Ureaplasma urealyticum was present in the vaginal smear of 15.4 percent of the 263 enrolled women, all of whom were healthy and in their second trimester of pregnancy. Of the women who tested positive for the microbe, 62.5 percent went on to have preterm labor, compared to 5.4 percent of women who tested negative. This situation is caused by the pro-inflammatory effects of Ureaplasma and Mycoplasma on the endothelium. Conclusion The maternal lower genital tract colonization by Ureaplasma and Mycoplasma increases the rate of preterm birth. The complications that lead to preterm birth due to infection by Ureaplasma and Mycoplasma were the premature rupture of the membrane and the precocious maturation of the uterine cervix.