OBJECTIVE: The purpose of this study was to determine the prevalence and clinical significance of microbial invasion of the amniotic cavity in patients presenting with cervical dilatation in the midtrimester of pregnancy. STUDY DESIGN: Amniocentesis for microbial studies was performed in women admitted with cervical dilatation ≥2 cm, intact membranes, and without active labor between 14 and 24 weeks of gestation. Amniotic fluid was cultured for aerobic and anaerobic bacteria, as well as for mycoplasmas. Gram stain was performed on all samples. RESULTS: The prevalence of microbial invasion of the amniotic cavity was 51.5% (17/33). The most common microbial isolates were Ureaplasma urealyticum, Gardnerella vaginalis, Candida albicans, and Fusobacterium sp. All patients with microbial invasion of the amniotic cavity had complications. Patients who underwent cervical cerclage in the presence of a positive amniotic fluid culture had rupture of membranes, clinical chorioamnionitis, or pregnancy loss. On the other hand, the prognosis of patients with a negative amniotic fluid culture was better than that of patients with a positive culture. Of 16 patients with a negative amniotic culture, nine were delivered at >34 weeks. CONCLUSIONS: (1) Microbial invasion of the amniotic cavity occurs frequently in women presenting with cervical dilatation in the midtrimester; (2) the microbiologic state of the amniotic cavity is an important prognostic factor for pregnancy outcome; (3) amniocentesis to determine the microbiologic characteristics of the amniotic cavity should be considered before a cerclage is placed in women presenting with cervical dilatation in the midtrimester. (Am J Obstet Gynecol 1992;167:1086–91.)

Infection and labor