MEDICATIONS: ANTIBIOTIC TREATMENT FOR BV AND TRICHOMONAS IN HIGH-RISK PREGNANT WOMEN DOES NOT PREVENT PRETERM BIRTH

March 30, 2005 — Contrary to the findings of earlier studies, screening high-risk pregnant women and treating them with antibiotics for bacterial vaginosis (BV) or trichomonas vaginalis does not help prevent preterm birth, according to a new meta analysis published in the April issue of Obstetrics & Gynecology. In fact, the analysis finds that treatment with the antibiotic metronidazole for trichomonas (a sexually transmitted disease) among pregnant women actually increases the incidence of preterm birth.

The preterm birth rate in the US has increased over the past several decades and is a significant cause of infant death and illness. Preterm birth is defined as birth occurring before 37 weeks of gestation. It has been recognized that infection of the fetal membranes and/or the amniotic fluid is associated with preterm birth. If BV and trichomonas are associated with preterm labor and birth, then it was thought that antibiotic treatment to cure these infections would prevent preterm birth. Three recently published meta analyses concluded that while there is no benefit to screening and treating BV among the general obstetric population, all suggest there is a benefit to screening and treating pregnant women at high risk for preterm birth.

Canadian researchers reviewed all randomized control studies to date that were published in English and that included pregnant women treated for either BV or trichomonas during the second or third trimester and who had intact membranes and were not in labor. The researchers found that while treatment with antibiotics (either metronidazole or clindamycin) for BV among pregnant women (both high risk and non-high risk) consistently reduced the risk of persistent BV, it did not reduce the risk of preterm birth at less than 37 weeks nor did it have any benefit to the newborn. The data available at this time also suggest that there is no benefit to treating pregnant women for trichomonas to prevent preterm birth.

The researchers conclude that there is no evidence that supports the screening and antibiotic treatment of BV in pregnant women in the second or third trimester, either in the general population or in high-risk women, to prevent preterm birth. However, studies are needed to see if this applies to screening and treatment of women in the first trimester of pregnancy. There is also no evidence that supports the treatment of trichomonas in pregnancy, and there is some evidence that it may actually be harmful.