The major difference between ParaGard and Mirena is that ParaGard is an IUD that does not have any hormones, according to Dr. Sara Kennedy. The makers of ParaGard say the IUD contains a small copper filament that interferes with fertilization and sperm movement, preventing pregnancy without releasing hormones.
Mirena releases a small amount of progesterone each day. Unlike many birth control pills, Mirena does not contain any estrogen. Dr. Kennedy says the lack of estrogen results in Mirena causing fewer side effects than birth control pills.
Women often experience menstrual changes due to the progesterone in Mirena, according to Dr. Kennedy. Irregular bleeding typically occurs for three to six months. Once the irregular bleeding stops, some women have light periods, and others stop having periods completely.
Because ParaGard does not contain any hormones, it does not cause a woman to stop menstruating, explains Dr. Kennedy. Instead, ParaGard typically causes longer, heavier periods for up to six months after insertion. Women who use ParaGard may also experience increased cramping during the first few months. After this adjustment period, a woman's menstrual flow typically returns to normal.
Dr. Kennedy notes that another difference between the two IUDs is how long they last. Hormone-containing Mirena lasts for up to five years, while the ParaGard with copper lasts up to 12 years.