Placental Ureaplasma Infection Linked to Preterm Birth


LISBON — Women who give birth prematurely have a markedly increased prevalence of placental Ureaplasma urealyticum infection, Dr. Leonard E. Weisman reported at the 12th International Congress on Infectious Diseases.

This novel observation raises the possibility that a significant fraction of preterm births might be preventable if a practical means of prospectively identifying women placentally colonized or infected with U. urealyticum can be developed. Their detection prior to labor would permit timely antimicrobial therapy aimed at clearing their placental infection—and deactivating their preterm birth trigger, Dr. Weisman explained in an interview.

This strategy would not provide a total answer to the enormous problem of preterm birth, which has a multitude of potential causes. But it would take a substantial bite out of the problem.

It has been estimated that reproductive tract infections play a role in up to 60% of all preterm births. Placental U. urealyticum probably figures in a substantial minority of those infections, said Dr. Weisman, professor of pediatrics at Baylor College of Medicine and director of the perinatal center at Texas Children's Hospital, Houston.

He presented a case-control study involving 58 women at three hospitals in the Texas Medical Center who gave birth at 30 weeks' gestation or earlier. The control group consisted of 194 randomly selected women who had a term birth. Twenty-seven women in the control group were classified as complicated controls, meaning they had a term delivery involving premature rupture of membranes, maternal fever, prolonged rupture of membranes lasting longer than 18 hours, and/or clinical endometritis or chorioamnionitis.

All study participants had their placental chorion cultured for U. urealyticum and group B streptococcus using sterile technique. The prevalence of U. urealyticum colonization/infection was significantly greater in women with preterm birth or a complicated term delivery than in those with an uncomplicated term birth (see box).

The medical literature describes numerous unsuccessful attempts to reduce the incidence of preterm birth via antibiotic therapy.

These past disappointments may have been due to reliance on easily assessable lower genital tract infection as the indication for treatment, when it's actually placental involvement that matters, Dr. Weisman said at the congress sponsored by the International Society for Infectious Diseases.

He and his Baylor coworkers recently launched a prospective trial to test their hypothesis that some identifiable aspect of vaginal colonization with U. urealyticum—one candidate is Ureaplasma biovar type—will correlate with placental colonization. If that indeed turns out to be the case, the next step will be a treatment study aimed at clearing placental infection in order to reduce the rate of preterm birth.

The best drug for use in this setting remains unclear. Erythromycin has often been used in trials aimed at eradicating vaginal infection; however, resistance of U. urealyticum to this antibiotic is a growing problem.

Tetracyclines show the best efficacy in vitro but are inappropriate for use in pregnancy. One of the quinolones may turn out to be the best choice, Dr. Weisman said.

Next Article: