<s>[INST] I have a merida IUD. I have not had a period in 2 1/2 years but recently started spotting. I have taken benedryl to sleep for the last five years and recently decided to wean myself off and switch to melatonin. What are the risks of pregnancy while on the IUD and how does it affect ovulation. Thank you [/INST] Thank you for the question and I am happy to help.The Mirena IUD secretes progesterone in the inside of the uterus and prevents the uterine lining from responding to the normal cycle of hormones produced by your ovaries.  The Mirena IUD does not affect ovulation - you are still ovulating while it is in place.  The main way that this IUD works is by thickening cervical mucous and creating a barrier for sperm to get to the fallopian tube.  When the IUD has been in place for a long time, it might cause thinning of the uterine lining which can lead to breakthrough bleeding.  This can be prevented by putting you on a short course of progesterone or birth control pills.  The risks of pregnancy while on the Mirena IUD are extremely small.  They are not zero, however, and you should take a pregnancy test.I hope that this helps and good luck to you!Dr. Tim </s>