birth control
"I had my copper IUD placed while I was on my period.  Your uterus is dilated during your period making insertion easier. The insertion felt like the onset of birthing contractions and it lasted about 30 seconds to 1 minute. I have read a lot of reviews where girls bleed for weeks after insertion. My doctor said that usually only happens if you are coming off of certain types of birth control, but the IUD should not be the cause of it. He was right. Prior to insertion I was not on birth control for a very long time. I had a heavier period after insertion and I cramped a bit that day.  My period lasted for my usual amount of time.  I had relations about a week after with no complication with above if not average size and he did not feel it."