Influence of the normal menstrual cycle on vaginal tissue, discharge, and microflora

The objective of this study was to examine genital tissue, vaginal fluid, a nd vaginal microbial flora at 3 phases of the menstrual cycle in asymptomat ic women. Vaginal examinations were performed 3 times in 74 women: at the m enstrual phase (days 1-5), the preovulatory phase (days 7-12), and the post ovulatory phase (days 19-24), Flora of 50 women without bacterial vaginosis (BV) was analyzed separately from flora of 24 women with BV: The volume of vaginal discharge increased and the amount of cervical mucus decreased ove r the menstrual cycle. Among subjects without BV, the rate of recovery of a ny Lactobacillus changed little (range, 82% to 98%; P = .2); however, a sma ll increase occurred in the rate of recovery of heavy (3+ to 4+ semiquantit ative) growth of Lactobacillus over the menstrual cycle (P = .04). A linear decrease occurred in the rate of recovery of heavy growth of any non-Lacto bacillus species, from 72% at days 1-5 to 40% at days 19-24 (P = .002). A l inear decrease also occurred in the rate of recovery of Prevotella species, from 56% on days 1-5 to 28% on days 19-24 (P = .007), while a small linear increase occurred in the rate of recovery of Bacteroides fragilis (P = .05 ). Among subjects with BV, the only significant change was an increase in t he rate of recovery of Lactobacillus, from 33% at days 1-5 to 54% at days 1 9-24 (P = .008). Among all subjects, the rate of recovery of heavy growth o f Lactobacillus increased over the menstrual cycle and, in contrast, the co ncentration of non-Lactobacillus species tended to be higher at menses, whi ch is evidence that the vaginal flora becomes less stable at this time.