The efficacy of prophylactic erythromycin in preventing vertical transmission of Ureaplasma urealyticum.

To determine if prophylactic erythromycin alters the vertical transmission rate of Ureaplasma urealyticum. Randomized prospective study of 51 singleton pregnancies between 22 and 35 weeks' gestation with preterm premature rupture of membranes or preterm labor. Patients received oral erythromycin for 7 days in addition to routine prophylactic intravenous ampicillin or ampicillin alone. Lower genital colonization with U. urealyticum was 33 of 51 (65%). Vertical transmission of U. urealyticum was 25% (3 of 12) in the erythromycin group and 4 of 17 (24%) for the controls. The average interval from randomization to delivery was 303.5 hr in the erythromycin group and 70.9 hr for controls (p = 0.04). Although not statistically significant, histologic chorioamnionitis in patients colonized with Ureaplasma was lower in the erythromycin group (3 of 12, 25%) compared to the controls (10 of 17, 59%). Prophylactic erythromycin does not decrease vertical transmission of Ureaplasma. It may decrease the incidence of histologic chorioamnionitis and increase the latency period.