U. urealyticum has been implicated in a variety of obstetric and neonatal diseases including preterm labor, preterm premature rupture of membranes (PPROM), chorioamnionitis, postpartum fever and endometritis, congenital pneumonia, bacteremia, meningitis, and bronchopulmonary dysplasia/chronic lung disease (BPD/CLD). The presumed mechanisms of infection include fetal exposure to ascending intrauterine infection, passage through an infected birth canal, and hematogenous dissemination through the placenta into umbilical vessels. This exposure leads to colonization of the skin, mucosal membranes, and respiratory tract, and sometimes leads to dissemination into the bloodstream and central nervous system (CNS). Phospholipases and cytokines produced through the inflammatory response can trigger uterine contractions and premature birth. Ureaplasmal infection of the respiratory tract in the newborn promotes a proinflammatory cytokine cascade with increase in tumor necrosis factor α, interleukin (IL)-1β, and IL-8. These cytokines recruit neutrophils to the lungs and intensify the inflammatory cascade, which damages the premature lung and impairs future alveolar development.