I think they can actually. Cats too. 2 stories:
When my friend started menstruatung the first time and didn´t know it yet, her cat was running after her screaming. He stopped as soon as she noticed it after going to the bathroom.
A dog I knew had been treated badly by children when she was little and didn´t like kids after that. She used to nibble/bite in the back of the knees. I was there during the summers and when year I came back after I got by period for the first time and she was friendly. She saw me as a adult. So maybe they can smell the hormones changing.
<Added Nov 9 2010>
Definitely. I know now when I am about to start mine because of my female dog. The day before she constantly sits at my feet and stares at me through half eyes and whines. At first wondered what on earth was going on but after about 3 of my cycles I saw the pattern so I now know when my cycle is coming .... which is great because mine isn't regular ! Hope this answers your question :)
Dogs have 20 times the number of smell receptors in their noses than humans. So yes a dog can smell when a women is menstruating.
No, it is not permissible for a Muslim woman to pray while menstruating.
no
In the Bible, there is no specific prohibition against women attending church while menstruating.
when not menstruating
body temp. rise
Islam allow oral sex but not if the woman is menstruating.
Some orthodox men will not touch a woman because they do not know if she is menstruating or not. If they were to touch a menstruating woman, they would have to undergo a ritual before they could engage in certain activities, such as public prayer in a synagogue. non-orthodox Jews do not follow this law.
No. If you are pregnant and bleeding you should contact your Dr right away.
Urinalysis should not be performed while a woman is menstruating or having a vaginal discharge
The average woman will use 15,000 pads or tampons in her menstruating life.
A woman should NEVER use tampons when not menstruating - thus a pregnant woman wouldn't be using tampons to begin with.