Figure 4. Vaginal pH correlates with Lactobacillus abundance and peak fertility in humans.

(A) Bars show mean (+SEM) of vaginal pH for women as a function of number of years before or after peak fertility, which was taken to be 25 years of age for all subjects. (B) Vaginal pH is significantly associated with Lactobacillus abundance (Kendall’s Tau test; τ = −0.38; P = 3.2×10⁻⁸). Statistical differences between groups were assessed using the Mann-Whitney U test.