How They Work
IUDs and IUSs have been found to create a low-grade infection in the uterus, which may interfere with sperm mobility and block sperm from passing into the Fallopian tubes and joining with an ovum. The IUS also time-releases progesterone into the lining of the uterus, which alters the lining, making implantation difficult.
IUDs/IUSs must be inserted by a healthcare provider, typically midcycle, when the cervix is softer. A string hangs down from the cervix, and the woman must check for the string once a month to make certain the IUD/IUS is still in place. Some men have reported that they can feel this string during intercourse. Because of the risk of pelvic inflammatory disease and sterility, IUDs/IUSs are not recommended for college-aged students who have not had children. Some IUDs can be left in place for up to 12 years, whereas others need to be changed yearly. It is recommended that the Mirena IUS be replaced every 5 years.
Both of the intrauterine contraceptives provide some of the highest overall effectiveness rates, ranging from 99.2% to 99.9%. These rival the rates of tubal sterilization (Grimes,
2004) , which we will discuss later in this chapter. Typically the Mirena IUS has a higher effectiveness rate than the Copper T (Grimes, 2004). Effectiveness also depends on the age of the woman and her past pregnancy history. A woman who has never been pregnant is more likely to expel the IUD/IUS through her cervix.
IUDs/IUSs are the least expensive method of contraception over time, and they do not interfere with spontaneity. In addition, they have long-lasting contraceptive effects. The Mirena IUS decreases menstrual flow because the progesterone reduces the endometrial buildup—20% of women using the Mirena will have no bleeding at all after 1 year of use (Dubuisson & Mugnier, 2002). The GyneFix IUD also has been found to reduce menstrual flow and cramping.