A program of screening for and treating asymptomatic vaginal infections was associated with a significant reduction in preterm birth and miscarriage in a randomized controlled trial of more than 4,000 women.
Researchers randomized 4,155 pregnant women to receive either screening and treatment or screening and no treatment. The screening was administered at a routine prenatal visit between week 15 and 19 of pregnancy, and the women were screened for bacterial vaginosis, Candida, or Trichomonas vaginalis, or combinations of any of the three, noted Dr. Herbert Kiss and his associates at the University of Vienna, Austria (BMJ 2004;329:371).
About 80% of the women had no vaginal infection; 13% had Candida colonization, 7% had bacterial vaginosis, and 1.5% had a combination of bacterial vaginosis and candidiasis. Three women had a trichomonal infection and two had a combination of bacterial vaginosis and trichomoniasis.
Women in the intervention group who had an infection received the appropriate treatment from their obstetricians. They were evaluated at the next prenatal visit. Those with persistent infection received additional treatment. Screening results for women in the control group were withheld from those obstetricians so that they did not influence her standard prenatal care.
The rate of spontaneous preterm birth was 3% in the intervention group and 5.3% in the control group. The rate of preterm infants weighing 2,500 g or less was significantly lower in the intervention group than in the control group (1.7% vs 3.5%). The number of spontaneous preterm births in the lower weight categories was 50% lower in the intervention group. The rate of late miscarriages was also reduced by 50%.
There were no significant differences between groups in intrauterine death, meconium passage, necrotizing enterocolitis, neonatal sepsis, or neonatal death.
A subgroup analysis showed the greatest treatment effect occurred in the women with a diagnosis of vaginal candidiasis. The number of spontaneous preterm births was almost three times higher in women who were not treated for candidiasis than in those who were treated (20 births vs. 7 births). A much smaller effect was seen in the group with bacterial vaginosis; there were eight spontaneous preterm births in the untreated women and five in the treated women.
Candidiasis has not been associated with preterm birth. However, the researchers suggested, obstetricians who knew their patients had a vaginal infection may have followed them more closely, thus accounting for the good results in the treated group.
In an accompanying editorial, Dr. Anna Alanen agreed that something other than infection treatment probably accounted for the improved outcomes in the intervention group. “The study … is in agreement with most previous studies concerning the failure of antenatal treatment of bacterial vaginosis to prevent preterm birth. The rate of preterm birth was, however, significantly lower in the intervention group, implying that factors connected to the screening program, including the role of candidiasis, deserve further studies.”