We can no longer ignore the fact that exposure to microbes in the womb is more common than previously thought and may even be a normal part of human pregnancy. As the matter of fact, the evidence is emerging to suggest that common body microbes such as lactobacilli may play a beneficial role in body sites traditionally viewed as being sterile.

While we can only speculate on what functions lactobacilli might perform in the healthy ovary or follicular fluid, other studies suggest a role for lactobacilli in conception.

The failure of the sperm–egg conception process is not infrequent, and the study of infertility has provided useful insights into the details of the fertilization process.

Of infertility cases, one-third remain unexplained, while the others are attributed to infection or to anatomical and physiological problems.

Some studies investigating unexplained infertility have shown the presence of lactobacilli in human follicular fluid. These bacteria, known for their beneficial effects on health and their usage in food, have been recently associated with embryo maturation and transfer.

One study found that lactobacilli can protect human spermatozoa from radical oxygen species in the presence of vaginal disorders, thereby improving the fertilization potential of the female host.

Vitamins are critical for the first 1000 days of life, most notably folic acid for brain and nerve system development. A number of these vitamins can be produced by bacteria such as lactobacillus which produces vitamin K and facilitates digestion.

Could this be a part of the reason why they are so important? More can be found here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4282787/