Some essential oils may inhibit blood clotting. This means, the blood can become thin and you can be at risk for bleeding out during surgery. Not everyone will need to be overly concerned about knowing this information, but for some, the risks can be fatal. Important information. Mirena should not be used during pregnancy. You should not use a Mirena IUD if you have abnormal vaginal bleeding, a pelvic infection, certain other problems with your uterus or cervix, or if you have breast or uterine cancer, liver disease or liver tumor, or a weak immune system. Vagifem 10 micrograms vaginal tablets - Patient Information Leaflet (PIL) by Novo Nordisk Limited.