Recently I was put on low dose estrogen to help offset symptoms of the onset of menopause. Up until the last few days, I've not had a period since January. I started bleeding like what I'd experience with a normal period previously. I then had a fair amount of cramping followed by the passing of a clot (1-2 inches in diameter). The clot was unusual as it had what looked like muscle tissue in it as well. I took it to my doctor who has sent it in for a biopsy. He stated that it was membranes. What is this and is it something to be concerned about? Thanks for your help.