Whats the side effects of using micronor (norethindrone)?

Possible bleeding. Most birth controll pills contain both estrogen and Progesterone which is how the pills help establish a balance and thus, facilitate the regulation of menstruation. Micronor (norethindrone) only contains progsterone, and is used for patients who may have contraindications to estrogen or for breastfeeding patients (estrogen drys up milk production). Therefore, expect some spotting to irregular bleeding.