When girls are born, their bodies are very high in oestrogen. High oestrogen means that there are a abundant lactobacilli and other beneficial bacteria throughout the baby’s vagina, since oestrogen stimulates vaginal cells to produce glycogen – food for lactobacilli.
Babies get a good dose of good bacteria from a vaginal birth, as they pass through the vaginal canal. The mucous from the mother is rich in good bacteria, and it goes into the mouth, nose, ears and eyes of the baby. This is a good start to life, but can also be pretty easily replaced using probiotics for babies on the nipple of a breast or bottle if the baby came out via a C-section, or smooshing healthy vaginal fluids onto a bottle or nipple.
This means that a baby girl has lots of lactobacilli or other beneficial bacteria in her vagina, but as the baby grows, this oestrogen dissipates and the bacteria counts drop back to almost nothing, due to lowered glycogen levels.
As the girl grows, the bacteria stays very low until she hits puberty and the oestrogen starts up again. This production of glycogen in the vagina has a protective effect by encouraging the growth of good bacteria that keeps the vagina healthy during reproductive years.
Lack of oestrogen is the primary difference between a girl’s vagina and an adult woman’s vagina. Oestrogen has many effects on the whole vaginal area, including the shape, size and colour of the labia, and fluid production in the vagina. The hormones that kick in at puberty change the look of the vagina and vulva, when the body kicks into gear for fertility.