First of all..... A Woman's period isn't an illness that you can get... You're male... Males can catch periods. A period refers to the time each month that the uterus expels the blood that has been building up in the lining of the uterus in preparation of a possible pregnancy. There is no illnesses involved. If you and your wife are ok with intercourse at this time of the month that its ok to do so. I think maybe it would do you some good to call your local community college and sign up for a sex education course, at 27 you should know what a period is.
There are two side effects of having sex with a partner that is on the rag. One is that your unit will change color slightly until you shower and the second is it will smell terrible until you shower. Other than that, less work to lubricate. Hit it hard my friend!!
I am female and I have never heard of anyone that has gotten ill from this. If your wife has a disease and you have intercourse you will more that likely get it period or no period. I guess you don't have your red wings?
The side effects are the same during a period as they are without a period.