have a low risk of side effects, though some persons and organizations disagree. Female sterilization is a more significant operation than vasectomy, and has greater risks; in industrialized nations, mortality is 4 per 100,000 tubal ligations, versus 0.1 per 100,000 vasectomies. After IUD insertion, users may experience irregular periods in the first 3–6 months with Mirena, and sometimes heavier periods and worse menstrual cramps with ParaGard. However, continuation rates are much higher with IUDs compared to non-long-acting methods. A positive characteristic of IUDs is that fertility and the ability to become pregnant returns quickly once the IUD is removed. Because of their systemic nature, hormonal methods have the largest number of possible side effects. Combined hormonal contraceptives contain estrogen and progestin hormones. They can come in formulations such as pills, vaginal rings, and transdermal patches. Most people who use combined hormonal contraception experience breakthrough bleeding within the first 3 months. Other common side effects include headaches, breast tenderness, and changes in mood. Side effects from hormonal contraceptives typically disappear over time (3-5 months) with consistent use. Less common effects of combined hormonal contraceptives include increasing the risk of deep vein thrombosis to 2 to 10 per 10 000 women per year and venous thrombotic events (see venous thrombosis) to 7 to 10 per 10,000 women per year. Hormonal contraceptives can come in multiple forms including injectables. Depot medroxyprogesterone acetate (DMPA), a progestin-only injectable, has been found to cause amenorrhea; however, the irregular bleeding pattern returns to normal over time. DMPA has also been associated with weight gain. Other side effects more commonly associated with progestin-only products include acne and hirsutism. Compared to combined hormonal contraceptives, progestin-only contraceptives typically produce a more regular bleeding pattern. Sexually transmitted disease prevention Male and female condoms provide significant protection against sexually transmitted diseases (STDs) when used consistently and correctly. They also provide some protection against cervical cancer. Condoms are often recommended as an adjunct to more effective birth control methods (such as IUD) in situations where STD protection is also desired. Other barrier methods, such as diaphragm may provide limited protection against infections in the upper genital tract. Other methods provide little or no protection against sexually transmitted diseases. Effectiveness calculation Failure rates may be calculated by either the Pearl Index or a life table method. A "perfect-use" rate is where any rules of the method are rigorously followed, and (if applicable) the method