ABSTRACT
The purpose of this prospective investigation was to evaluate the microbiology of
the lower genital tract and amniotic fluid in asymptomatic women with preterm labor.
We limited inclusion in the study to patients at 20 to 36 weeks' gestation whose membranes
were intact and whose cervix was at least 50% effaced and 2 cm dilated. At the time
of admission, we obtained an endocervical specimen for culture for Neisseria gonorrhoeae and for enzyme-linked immunoabsorbent assay for Chlamydia trachomatis and a vaginal specimen for culture for group B streptococci (GBS). We also performed
transabdominal amniocentesis to collect amniotic fluid for Gram's stain, latex fixation
test for GBS, and aerobic and anaerobic cultures. All patients received parenteral
tocolytics. Women who had an immature lecithin to sphingomyelin ratio also received
betamethasone. Only 1 of 72 women (1.4%, 95% confidence interval 0 to 4.1%) had a
positive amniotic fluid culture. One patient (1.4%) had a positive Gram's stain, and
two (2.8%) had positive latex fixation tests. None of these individuals subsequently
had a positive culture. Eight women (11.1%) had positive tests for chlamydia, and
four (5.5%) had positive vaginal cultures for GBS. None of the patients developed
clinical evidence of chorioamnionitis, and only one had puerperal endometritis. None
of the neonates had any complications due to infection. We conclude that, in our population,
intra-amniotic infection is not a common cause of preterm labor in asymptomatic patients
with intact membranes and that amniocentesis should not be performed routinely to
assess the bacteriology of the amniotic fluid.
