• Irregular menstrual pattern: irregular bleeding and spotting is common in the first three to six months of use. After that time periods become shorter and lighter, and 20% of women stop having periods after one year of use. The average user reports 16 days of bleeding or spotting in the first month of use, but this diminishes to about four days at 12 months. • Cramping and pain: many women feel discomfort or pain during and immediately after insertion. Some women may have cramping for the first 1–2 weeks after insertion. Expulsion is more common in younger women, women who have not had children, and when an IUD is inserted immediately after childbirth or abortion. • Perforation: Very rarely, the IUD can be pushed through the wall of the uterus during insertion. Risk of perforation is mostly determined by the skill of the practitioner performing the insertion. For experienced medical practitioners, the risk of perforation is one per 1,000 insertions or less. With postpartum insertions, perforation of the uterus is more likely to occur when uterine involution is incomplete; involution usually completes by 4–6 weeks postpartum. If PID does occur, it will most likely happen within 21 days of insertion. The device itself does not increase the risk of infection. Thus, any issues with ovarian cysts are not of a clinically relevant nature. Most of these follicles are asymptomatic, although some may be accompanied by pelvic pain or dyspareunia. In most cases the enlarged follicles disappear spontaneously after two to three months. Surgical intervention is not usually required. • Mental health changes including: nervousness, depressed mood, mood swings • Weight gain • Breast pain, tenderness • May affect glucose tolerance Various thread collector devices or simple forceps may then be used to try to grasp the device through the cervix. In the rare cases when this is unsuccessful, an ultrasound scan may be arranged to check the position of the coil and exclude its perforation through into the abdominal cavity or its unrecognised previous expulsion.
Cancer According to a 1999 evaluation of the studies performed on progestin-only birth control by the International Agency for Research on Cancer, there is some evidence that progestin-only birth control reduces the risk of endometrial cancer. The IARC in 1999 concluded that there is no evidence progestin-only birth control increases the risk of any cancer, though the available studies were too small to be definitively conclusive. Progesterone is a hormone in the endometrium that counteracts estrogen driven growth. Very low levels of progesterone will cause estrogen to act more, leading to endometrial hyperplasia and adenocarcinoma. Researchers cautioned against causal interpretation from this study, citing
confounding effects, methodological concerns and a 2020 meta-analysis of randomized controlled trials which showed no increased risk.
Bone density No evidence has been identified to suggest Mirena affects
bone mineral density (BMD). Two small studies, limited to studying BMD in the forearm, show no decrease in BMD. One of the studies showed at seven years of use, similar BMD at the midshaft of the
ulna and at the distal
radius as nonusers matched by age and
BMI. In addition, BMD measurements were similar to the expected values for women in the same age group as the participants. The authors of the study said their results were predictable, since it is well established that the main factor responsible for bone loss in women is
hypoestrogenism, and, in agreement with previous reports, they found
estradiol levels in Mirena users to be normal. ==Composition and hormonal release==