been explained have some forms of severe liver disease. Women should not use combined hormone contraceptives (CHC) if they have migraines with auras. A full list of contraindications can be found in the WHO Medical Eligibility Criteria for Contraceptive Use 2015 and the CDC United States Medical Eligibility Criteria for Contraceptive Use 2016. Side effects Irregular bleeding and spotting: Many women will experience some type of irregular, unpredictable, prolonged, frequent, or infrequent bleeding. Some women also experience amenorrhea. For some women, prolonged bleeding will decline after the first three months of use. However, other women may experience this bleeding pattern through all five years of use. While these patterns are not dangerous, they are the most common reason that women give for discontinuing the use of the implant. After removal, bleeding patterns return to previous patterns in most women. Insertion complications: Some minor side effects such as bruising, skin irritation, or pain around the insertion site are common. However, there are some rare complications that can occur, such as infection or expulsion. In some cases, a serious complication occurs when the provider fails to insert, and the rod is left in the inserter. An Australian study reported 84 pregnancies as a result of such failure. Migration: Although very rare, the rod can sometimes move slightly within the arm. This can make removal more difficult. It is possible that insertion in the same site as a previous implant increases the likelihood of migration. Rods can be located only through high-frequency ultrasound or magnetic resonance imaging (MRI). It can be located using traditional X-ray or CT-scan because of the inclusion of barium sulphate. There have been rare reports of implants having reached the lung via the pulmonary artery. Correct subdermal insertion over the triceps muscle reduces the risk of these events. Possible weight gain: Some women may experience slight weight gain when using the implant. However, current studies are not conclusive because they do not compare the weight of women using implants with a control group of women not using the implant. The average increase in body weight in studies was less than 5 pounds (2,25 kg) over 2 years. Ovarian cysts: A small portion of women using implants and other contraceptive implants develop ovarian cysts. Usually these cysts will disappear without treatment. Pregnancy: it is recommended that implants be removed if a pregnancy does occur. However, there is no evidence to