Predictive value for preterm birth of abnormal vaginal flora, bacterial vaginosis and aerobic vaginitis during the first trimester of pregnancy

Abnormal vaginal flora (AVF) before 14 gestational weeks is a risk factor for preterm birth (PTB). The presence of aerobic microorganisms and an inflammatory response in the vagina may also be important risk factors.The primary aim of the study was to investigate the differential influences of AVF, full and partial bacterial vaginosis, and aerobic vaginitis in the first trimester on PTB rate. The secondary aim was to elucidate why treatment with metronidazole has not been found to be beneficial in previous studies.Unselected women with low-risk pregnancies attending the prenatal unit of the Heilig Hart General Hospital in Tienen, Belgium, were included in the study.At the first prenatal visit, 1026 women were invited to undergo sampling of the vaginal fluid for wet mount microscopy and culture, of whom 759 were fully evaluable. Abnormal vaginal flora (AVF; disappearance of lactobacilli), bacterial vaginosis (BV), aerobic vaginitis (AV), increased inflammation (more than ten leucocytes per epithelial cell) and vaginal colonisation with Candida (CV) were scored according to standardised definitions. Partial BV was defined as patchy streaks of BV flora or sporadic clue cells mixed with other flora, and full BV as a granular anaerobic-type flora or more than 20% clue cells. Vaginal fluid was cultured for aerobic bacteria, Mycoplasma hominis and Ureaplasma urealyticum. Outcome was recorded as miscarriage