Objective: The objective of this study was to assess whether antibiotic
therapy plus tocolysis given to women in preterm labor would prolong pregnancy
compared with tocolysis alone.
Methods: A randomized, double-blind trial of intravenous
mezlocillin and oral erythromycin therapy vs. placebo was used in addition to
tocolysis among women in preterm labor ≤34 weeks gestation with intact
membranes. Amniocentesis was performed, and chorioamnionic membranes
were examined histologically and cultured for microorganisms after delivery.
Results: Clinical characteristics including gestational age at
enrollment, frequency of contractions, cervical Bishop's score, and white blood
cell count on admission were similar in the 2 groups. Antibiotic therapy was well tolerated.
No significant differences in the interval to delivery, birth weight, and neonatal outcomes
were observed between the 2 groups. Women in the antibiotic group had a significantly
lower incidence of postpartum infections compared with women in the placebo group.
Patients with evidence of upper genital tract infection in either group had a significantly
shorter interval to delivery, lower gestational age at delivery, lower mean birth weight,
and increased neonatal hospitalization time.
Conclusions: Lack of an antibiotic effect on the gestational age
at delivery may be due to the low prevalence of upper genital tract infection among
unselected women in preterm labor, to advanced preterm labor unresponsive to antibiotic
therapy, or to an inability of antibiotics given alone to inhibit the cytokine response.
Further work is needed to identify markers of upper genital tract infection
among women in preterm labor and to evaluate other potential therapeutic interventions.