Noncontraceptive health benefits – for injectable contraceptives
Injectables have several health benefits in addition to preventing unintended pregnancy. They help to prevent endometrial and possibly ovarian cancer (see p. 15). They also may help women with anemia and sickle-cell disease. Also, like other contraceptive methods that prevent ovulation, such as combined oral contraceptives and, to a lesser extent, Norplant implants, injectables protect women against ectopic pregnancy, which can kill from sudden and severe internal bleeding if a fallopian tube ruptures. A few studies suggest other benefits of injectables, such as prevention of pelvic inflammatory disease (PID).
A contraceptive that increases hemoglobin levels is especially valuable in developing countries, where 20% to 40% of women suffer from iron-deficiency anemia (343). Several studies find that blood hemoglobin levels in DMPA or NET EN users increase (65, 121, 122, 201), although other studies find no change (1, 129). Progestin-only injectables may increase hemoglobin levels by reducing menstrual blood loss and by accelerating the formation of red blood cells and lengthening their survival (65, 121). Two studies of monthly injectables have found no change in hemoglobin levels (86, 108), while a one-year study of the monthly Mesigyna found a significant increase after the third injection (208).
Fewer Sickle-Cell Crises
Sickle-cell disease is caused by a defect in the structure of hemoglobin that leads to deformation of red blood cells into a sickle shape when deprived of oxygen. These cells block blood flow, causing painful sickle-cell crises. Sickle-cell disease is most common among blacks and causes at least 80,000 deaths worldwide every year (231).
Testosterone, progesterone, and progestins such as DMPA prevent sickle-cell crises, probably by stabilizing the membrane of red blood cells (139). In the only study of DMPA and sickle-cell disease, women using DMPA in a 2-year trial had significantly fewer crises than women given a placebo. Hematological tests found significant increases in total hemoglobin and red cell counts among DMPA users and significant decreases in the level of irreversibly sickled cells (65).
Possible Additional Benefits
Progestin-only injectables may help women with reproductive tract infections, epilepsy, or endometriosis. Evidence is slight, however, and further studies are needed.
Progestin-only injectables may help to prevent pelvic inflammatory disease. A WHO multinational study of 319 women with PID and 638 matched controls found that the risk of acute PID among DMPA or NET EN users was half that among nonusers, although the difference in risk was not significant because of the small sample (99). Injectables may protect against PID by thickening cervical mucus, preventing STD organisms from passing through the cervix.
Progestins have decreased the frequency of seizures in women with epilepsy (194, 359). Several studies have reported that the frequency of seizures in women decreases when progesterone levels are high during the menstrual cycle and increases when estrogen levels are high. In one study of 14 women who added oral and injected medroxyprogeterone acetate to their antiepileptic drugs for an average of 1 2 months, the frequency of seizures among 11 women who developed amenorrhea declined by 30%, from eight seizures per month before the addition to five after, a significant change (194).
Endometriosis causes painful menstruation and prolonged bleeding. Oral medroxyprogesterone at 20 to 30 mg a day is used to treat endometriosis (214). Clinical observation suggests that DMPA at the contraceptive dose decreases symptoms as well (154).
COPYRIGHT 1995 Department of Health
COPYRIGHT 2004 Gale Group