FIG 3.

Shift of the vaginal microbiome in pregnancy. Estrogen is one of the key factors that modulate the stability of the VMB. The concentration of estrogen and the stability of the VMB increase during pregnancy. The abundance of lactobacilli increases at the expense of species often related to vaginal dysbiosis, e.g., G. vaginalis, A. vaginae, and P. bivia. This shift in the VMB occurs early in pregnancy and is more pronounced in Black women. After delivery, estrogen levels, along with the stability of the VMB, decrease greatly, and the VMB converts from an optimal state to a state of dysbiosis, which often takes over 40 weeks to recover.