Association of Ureaplasma urealyticum in the placenta with perinatal morbidity and mortality.
We investigated the presence of ureaplasmas, mycoplasmas, chlamydiae, fungi, aerobic and anaerobic bacteria, and cytomegalovirus in fetal membranes and evaluated their association with perinatal morbidity and mortality. We cultured 801 placentas from three groups of subjects (144 who died in the perinatal period, 452 neonates admitted to the intensive-care unit, and 205 controls). Ureaplasma urealyticum, Mycoplasma hominis, or both were isolated from 21 per cent of placentas of premature and term infants who died in the perinatal period, 25 per cent of those admitted to intensive care, and 11 per cent of controls. Gestational age and birth weight were inversely related to isolation of ureaplasma, and chorioamnionitis was positively related to isolation. The presence of ureaplasmas in the placenta suggests the transcervical migration of these microorganisms from the lower genitourinary tract. These data show a strong association between ureaplasma infection of the placenta and low birth weight of the neonate and suggest that the association is causal.