Editing Endometrium (section)

===Microbiome speculation===
The uterus and endometrium was for a long time thought to be sterile. The [[cervical mucus plug|cervical plug]] of mucosa was seen to prevent the entry of any [[microorganism]]s ascending from the vagina. In the 1980s this view was challenged when it was shown that uterine infections could arise from weaknesses in the barrier of the cervical plug. Organisms from the vaginal microbiota could enter the uterus during [[uterine contractions]] in the menstrual cycle. Further studies sought to identify microbiota specific to the uterus which would be of help in identifying cases of unsuccessful [[IVF]] and miscarriages. Their findings were seen to be unreliable due to the possibility of cross-contamination in the sampling procedures used. The well-documented presence of ''[[Lactobacillus]]'' species, for example, was easily explained by an increase in the vaginal population being able to seep into the cervical mucous.<ref name="Baker"/> Another study highlighted the flaws of the earlier studies including cross-contamination. It was also argued that the evidence from studies using germ-free offspring of [[axenic]] animals (germ-free) clearly showed the sterility of the uterus. The authors concluded that in light of these findings there was no existence of a [[microbiome]].<ref name="Microbiome"/>

The normal dominance of Lactobacilli in the vagina is seen as a marker for vaginal health. However, in the uterus this much lower population is seen as invasive in a closed environment that is highly regulated by female sex hormones, and that could have unwanted consequences. In studies of [[endometriosis]] ''Lactobacillus'' is not the dominant type and there are higher levels of ''[[Streptococcus]]'' and ''[[Staphylococcus]]'' species. Half of the cases of [[bacterial vaginitis]] showed a polymicrobial [[biofilm]] attached to the endometrium.<ref name="Baker"/>