Objective: The purpose of this study was to determine if azithromycin is effective in reducing lower genital colonization of Ureaplasma urealyticum in women with preterm labor or preterm premature rupture of membranes (PROM).
Methods: A randomized, double-blinded, placebo-controlled prospective study of 60 pregnancies was carried out between 22 and 34 weeks. Genital mycoplasma cultures were performed at the time of admission. Patients were randomized to receive either a single dose of azithromycin (four 250 mg capsules) or a placebo in addition to prophylactic intravenous ampicillin. Repeat cultures were done on undelivered patients 7 days after enrollment. The study had power to detect a 50% decrease in colonization.
Results: Overall, lower genital colonization was 47/59 (79.7%) for U. urealyticum. Seven days after enrollment, U. urealyticum was isolated in 14/15 (93.3%) of the azithromycin-treated cases and in 11/14 (78.6%) of the controls (RR = 1.19, 95% CI = 0.88-1.61). Vertical transmission of U. urealyticum was 3/15 (20%) in the azithromycin-treated cases and 5/10 (50%) for the controls (RR = 0.40, 95%, CI = 0.12-1.31).
Conclusion: These data suggests that a single 1 g dose of azithromycin is ineffective in reducing lower genital colonization with U. urealyticum.