In addition, the mobile skin of the penis is «grasped» by the ridges of the vaginal mucosa and held in place. (drmomma.org)
«The vaginal mucosa is very hormone sensitive, so once the mother's hormones are out of the baby's system, there will be a little bleeding. (webmd.com)
Experts have hypothesized that the thinning of the vaginal mucosa by progesterone (pictured) makes it easier for HIV to penetrate the vaginal wall in an uninfected woman, and, conversely, for an HIV - positive woman to infect her partner. (scientificamerican.com)