An Attempt to Classify Gram-Stained Vaginal Smears with a Nugent Score of 4 into Four Bacterial Morphotypes at First Prenatal Visit

It is controversial whether universal screening for bacterial vaginosis (BV) should be done in the early stages of pregnancy in order to prevent preterm birth. In particular, whether the intermediate vaginal flora type should be included in the group to be treated for BV. This vaginal smear type is a mixture of Lactobacillus and Gardnerella or Bacteroides spp. We examined three vaginal flora types, excluding the mixed-type, with a Nugent Score of 4 and evaluated their significance in achieving term delivery. The subjects were pregnant women who were examined at our Hospital between June 2009 and December 2010. Their vaginal swabs were taken at their first prenatal visit and were studied by Gram staining. The resulting Nugent Score 4 organisms were further classified into the following four types: mixed-type, gram-positive cocci type, Bifidobacterium type, and non-bacterial type. The clinical courses for all the types except “mixed-type” were followed-up. Among the 566 pregnant women, 58 (10.2%) had a Nugent Score of 4. There were 38 cases of mixed-type (65.5%), 3 cases of gram-positive cocci type (5.2%), 10 cases of Bifidobacterium type (17.2%), and 7 cases of non-bacterial type (12.1%). The three women with the gram-positive cocci type attained successful term delivery despite two of them experiencing GBS infection and requiring treatment with penicillin and tocolytics. Among the 10 cases of Bifidobacterium type, 5 cases were term delivery with no therapy, 3 cases were term delivery with metronidazole treatment and 2 cases were preterm birth with maternal complications. Among the 7 cases of non-bacterial type, 6 cases were diagnosed with preterm PROM, and 5 of them resulted in preterm birth despite prophylactic antibiotic therapy. Classification of smears with a Nugent score of 4 into four bacterial morphotypes may be effective, for required treatment may vary depending on the morphotype.