Purpose: to evaluate the relationship between bacterial vaginosis (BV) and spontaneous preterm delivery. Method: a total of 611 pregnant women from the general antenatal clinic of the "Clínica Obstétrica do Hospital das Clínicas da Universidade de São Paulo" were enrolled in this study. All pregnancies were dated by an early scan. Iatrogenic preterm deliveries were excluded. The presence of bacterial vaginosis was evaluated between 23 and 24 weeks of pregnancy by a Gram stain of the vaginal smear collected from the posterior vaginal wall using a sterile swab. Vaginal pH was also assessed from the lateral vaginal wall by a Universal 0-14 pH strip produced by Merck. Result: a complete follow-up was obtained in 551 patients and bacterial vaginosis was diagnosed in 103 (19%) cases. Among the patients with BV in the vaginal smear, 9.7% delivered before 37 weeks against only 3.2% in the group with normal vaginal smear (p=0.008). The sensitivity, specificity, accuracy and false-positive rate for preterm delivery in the presence of bacterial vaginosis on Gram stain of the vaginal smear were 41.7, 82, 80.2 and 18%, respectively, with a relative risk of 1.8 for preterm delivery. The mean vaginal pH in the group of positive BV was 4.9 and in the group with normal smear it was 4.3 (p=0.0001). Conclusion: bacterial vaginosis during pregnancy increases the risk for spontaneous preterm delivery, with a relative risk of 1.8.
Bacterial vaginosis; Preterm delivery; Prenatal diagnosis
