Screening for Low-Tract Genital Infections in Women with Threatened Preterm Labor: Which Role?

Objectives: The aim of this study was to evaluate the possible relationship between cultural specimens and preterm birth in women admitted for threatened preterm labor. Preterm birth is the leading cause of neonatal mortality and antenatal hospitalization; several risk factors including intrauterine infections have been identified, but its real causes remain poorly understood. Design: This is a retrospective, multicenter, cohort study including 250 women admitted for threatened preterm labor. Methods, Participants/Materials, Setting: All women admitted for threatened preterm labor, i.e., presenting with cervical changes and uterine activity before 37 weeks at the obstetrics unit of the hospitals of Modena, Monza, Carate, and Vimercate were included in the study. We excluded twin pregnancies and cases with preterm premature rupture of membranes at admission. Data about maternal history, pregnancy complications, cervical length, vaginal swabs, and urine culture at admission and gestational age at delivery were collected from clinical records in order to compare the incidence of preterm birth according to some known risk factors, cervical length, and microbiological test at admission. Results: 250 women were included in the study; preterm birth at less than 37 weeks occurred in 44.4% women admitted for threatened preterm labor. The incidence of preterm birth was not different between those with a positive or a negative vaginal swab (48.3 vs. 38.4%, p = 0.22) or positive versus negative urine culture (31.8 vs. 42.1%, p = 0.23) at admission. A shorter cervical length at admission was found in women with subsequent preterm birth (17 vs. 19.5 mm, p = 0.03). Cervical length <15 mm (OR 1.82, 95% CI: 1.03-3.23, p = 0.039) predicted the risk of preterm birth. Furthermore, only the history of a previous preterm birth (p = 0.02) and a previous uterine curettage (p = 0.045) was associated with preterm birth. Limitations: The observational and retrospective nature of the study and its small sample size are important limitations of the study. Moreover, women were not systematically or randomly assigned to the screening for vaginal or urinary infections. Conclusions: There is no evidence that the search for vaginal or urinary infections in women admitted for threatened preterm labor is helpful to identify those at increased risk of preterm birth. Although several studies have explored the role of screening for bacterial vaginosis in asymptomatic women and some studies evaluated vaginal or urinary infections in women with preterm birth, none of them focused on the possible role of microbiological specimens as a predictive tool in women admitted for threatened PTL. No association was found in our study, but prospective randomized controlled trials are required to confirm the results of this observation.