Amy, you don't have to use estrogen with PIO, but many centers do use it. If you are worried about the risk of blood clots then you can skip it, but I am not sure that the one patch every other day is a significant risk. I have heard of excessive estrogen (like those used perhaps during a medical FET) could cause a slight risk of the blood clots. I know you are self medicating, but can you discuss with your doctor? Maybe tell them you are looking at potential future cycles and wondering what their opinion is on using the patch? Let us know how you make out.