You mentioned some other subject to before. The role of micro-organisms such as candida ofcourse might play role as well. Semen contents can control the pressure in the female uterus. Element such as zinc or acetylcholine in semen might act as a modifier of present candida on the penile surface, changing them from yeast in hyphe form.
I had some yeast/fungi spots on my skin over the years. These were discolorations. If you compare the growth of a spot over a period of 24 hours you won't detect any increase in radius. These things were developing very slowly over the course of multiple days to weeks and were quite innocent.
The oral candida outbreak was completely different in terms of speed of growth and intensity. This one just developed from nothing to white layers on oral surfaces and when the surfaces were coated it started to form wires all within 1 day. It also hurts when I moved my mouth/tongue, there wasn't mucus left, all extremely dry. I used an anti-fungal gel, Daktarin, which helped but when I swallowed the stuff I became weak and literally dropped to the ground. It felt like my immune resistance was swept away. Perhaps some kind of hypersensitivity reaction, I don't know? This effect was new to my GP at that time compared to other patients who were using it. So I used the stuff the flush my mouth.
My feet are sensitive to fungi when in POIS. But this is slowly developing and not of much concern. I'm using vicks vaporub for that if I see some redness developing between toes or toenails getting affected.
I think it might have to do with temporary IL-17 decrease which fungi might take advantage of. Perhaps via Catecholamine/tryptophan/kyn pathways affecting the Treg/Th17 axis.
My aunt had a vaginal yeast infection when she was 16. She also got food sensitivities.
My mother gets a burning sensation by intravaginal contact with semen. Just like myself I can get a burning sensation from my own semen.
There might be some answers in here:
Manifestations of immune tolerance in the human female reproductive tract 50% of people with POIS are circumcised...
Source?
Perhaps a defect genetic mucosal/endothelial function then plays a role as well.
Maybe, see paper above for more potential mucosal reproductive tract related immune causes.
Oh yes before I forget. All the women with health problems in my family felt better during pregnancy.