dear,
if your question is that, can a disease get transmitted through contact of mentrual fluid with penis, as I can figure it out here?
The answer is yes.
However, the chance or the in risk in such transmission is low.
next issue is, which are the infections that are common?
Any stds,
hiv or
hepatitis.
Now the que of worrying arises, is when either one of you partner is infected.
As you have confirmed it on investigations, there is no infection or disease confirmed.
Therfore, my advice here is, that there is no reason to worry or to be concerned.
And yes, contact with menstrual fluid can transmit an infection.
Hope to have satisfied your concern.
Stay healthy, thank you.