Can UTIs shorten menstrual periods?

Urinary tract infections usually don't effect menstrual periods.  There is a possibility, that if you are on oral contraceptives, and are prescribed certain antibiotics for a urinary tract infection, that the hormone levels could be affected and thus the period lengthened of shortened.  This would not be common.  However, many other things can affect a period, including stress, a change in weight, and a change in environment, to name just a few.