The use of the polymerase chain reaction to detect bacteria in amniotic fluid in pregnancies complicated by preterm labor

OBJECTIVES: The purpose of this investigation was to determine the feasibility of using the polymerase chain reaction to detect bacteria in amniotic fluid and to compare pregnancy outcomes in subsets of women categorized by amniotic fluid culture, polymerase chain reaction, and interleukin-6 findings. STUDY DESIGN: Amniotic fluid from 54 pregnancies with preterm labor and no clinical evidence of intraamniotic infection was evaluated with use of the polymerase chain reaction, interleukin-6, and bacterial culture. Gestational age, newborn weight, and time between amniocentesis and delivery were compared between subsets of women categorized by these tests. RESULTS: With use of the polymerase chain reaction <100 bacteria per milliliter could be detected in amniotic fluid. A total of 55.5% of the amniotic fluid samples were polymerase chain reaction positive, whereas 9.2% of culture results were positive. Birth weights and gestational age at delivery were less and time from amniocentesis to delivery was shorter in the polymerase chain reaction-positive group (p < 0.05). Nine samples (15%) had elevated interleukin-6 concentrations; of these, six were polymerase chain reaction positive. CONCLUSIONS: The polymerase chain reaction is a sensitive means of detecting bacteria in amniotic fluid. These results provide further evidence of an association between preterm delivery and intraamniotic infection. Not all amniotic fluid samples with elevated interleukin-6 levels have bacteria detectable by the polymerase chain reaction. We anticipate that the polymerase chain reaction will provide another avenue for the detection of bacteria in amniotic fluid.