Infection and preterm birth

Preterm birth complicates 11% of all pregnancies in the United States and r emains a leading cause of infant mortality and long-term neurological handi cap. The majority of this morbidity and mortality is concentrated among the small subset of infants born before 32 weeks' gestational age and that hav e birth weights < 1500 g. Although the survival of these preterm infants ha s improved over the last 20 years, the rate of long-term handicap has not. Despite widespread use of preventive strategies, the rate of preterm birth is increasing. Therefore, the prevalence of long-term handicap attributed t o preterm birth also is increasing. Considerable data implicate a clinicall y silent upper genital tract infection as a key component of the pathophysi ology of a majority of early spontaneous preterm births, but a minority of preterm births that occur near term. This report reviews the current status of our understanding of the relationship between genital tract microbial i nfection and spontaneous preterm birth, the availability and usefulness of markers to identify women with such infections, and the results of recent p rospective randomized clinical trials of antibiotic therapy to prevent pret erm birth. Strengths and limitations of the trials are reviewed in relation ship to their value for guidance in clinical management strategies and dire ctions for future research are discussed.