The reported study investigates the relationship of genital infections, pathobiochemical findings and demographic data to preterm labor, premature rupture of membranes (PROM) and premature delivery. The predictability of chorioamnionitis, puerperal and neonatal infections by these parameters was evaluated concurrently. 301 patients were included in this study between July 1985 and June 1986. 147 of these patients were studied longitudinally during pregnancy, delivery and puerperium (longitudinal group). A second group consisted of 154 women who presented themselves on start of labor to the labor and delivery unit of our Department (peripartal group). The incidence of preterm labor and of PROM was 26%. The incidence of premature delivery, chorioamnionitis, puerperal and neonatal infection was 11.4%, 5.5%, 7.6% and 3% respectively. Cervical colonization with Mycoplasma hominis correlated positively with PROM (relative risk 2.2), premature delivery (3.9) and neonatal infection (6.9). Chorioamnionitis, premature delivery and puerperal infection were also significantly increased in patients with positive vaginal Ureaplasma urealyticum cultures during pregnancy and delivery. Premature delivery (2.8) and puerperal infection (4.0) were associated with a vaginal group B-Streptococci (GBS) colonization during pregnancy, as was a positive GBS culture during delivery associated with puerperal infection. Bacterial vaginosis also correlated positively with premature delivery (5.6) and puerperal infection. Preterm labor correlated negatively with the socioeconomic level, PROM correlated negatively with the marital status, positively with age, a history of cervical cerclage, conization or PROM during former pregnancies. Sexual intercourse more often than once weekly during the last month of pregnancy was also associated with an increased number of PROM. Gardnerella vaginalis, Candida and Trichomoniasis during pregnancy and delivery were associated with preterm labor and puerperal infections. Levels of maternal plasma fibrinogen concentrations in patients with PROM were elevated 48 hours after delivery in accordance to the characteristics of acute phase proteins. In contrast, the maternal PMN-granulocyte-elastase concentration was significantly elevated at time of delivery and 24 hours thereafter in those patients who developed puerperal infections. The derived positive predictive value was 26%, the negative 94.7%, respectively. The overall accuracy of the prediction was 83.1%. Six out of seven mothers with neonates treated because of neonatal infection showed significantly elevated plasma concentration of PMN-granulocyte-elastase.(ABSTRACT TRUNCATED AT 400 WORDS)