Injectable Contraception (Depo-Provera)
Depot medroxyprogesterone acetate (Depo-Provera® or DMPA) is an injectable synthetic hormone that prevents pregnancy for 13 weeks at a time. The hormone is like the one produced by the body (progesterone) to regulate the menstrual cycle. DMPA works mainly by preventing ovulation- the process by which an egg is released from the ovary. It also thickens the cervical mucus, which may keep sperm from joining with an egg.

Effectiveness
DMPA is a highly effective form of birth control. For every 1,000 women using DMPA, only 3 will get pregnant with typical 1st year use. Thus, it has much less than a 1% failure rate.

Proper Use
DMPA is injected into the muscle of the upper arm or buttock, where it dissolves slowly and is released into the body over time. The drug's contraceptive effect starts in 24 hours and lasts for up to 13 weeks after the injection. It is important to receive regular injections every 13 weeks and not to let any more than 13 weeks lapse between injections.

Side Effects
Most women will initially experience more total days of bleeding and spotting while using DMPA. With time, bleeding is likely to get lighter and less frequent. About half of all women on DMPA will have no bleeding after 1 year. DMPA may also cause weight gain, which averages about 4 - 5 pounds each year for the 1st 3 years, and then levels off. Greater attention to exercise and nutrition may help offset this weight gain. Other possible but less common side effects include breast tenderness, headache, and loss of libido. It is important to note that after the last DMPA injection, the ability to conceive may be delayed. The average time to get pregnant is up to 12 months after the last DMPA injection. There is absolutely no permanent effect on fertility (the ability to conceive).

One study has shown a slight loss of bone density with DMPA use. It is unclear whether this loss is reversible after discontinuation. More studies are needed to see if there are any effects of DMPA on osteoporosis (bone loss). A recent World Health Organization study did not show any increase incidence of breast cancer or any other kind of cancer.

Contraindications to DMPA Use
You should not use DMPA if you have blood clots in the lungs or legs, cancer of the breast, unexplained vaginal bleeding, and/or impaired liver function. Other medical conditions such as depression, migraine headaches, diabetes or certain heart disorders may make another method of birth control preferable.

Advantages
DMPA is a safe, reliable, long-term method which does not need to be taken daily. It usually reduces menstrual cramps and, with time, reduces the amount of menstrual flow. It may protect against endometrial (uterine) cancer and even ovarian cancer. It can be used while breastfeeding. Some women who cannot take the birth control pill because of its estrogen content are able to take DMPA. Women with sickle cell anemia or epilepsy may actually do better with DMPA than with any other hormonal birth control method.

Disadvantages
Side effects, as listed above, may last until the shot wears off. Irregular bleeding and weight gain tend to be the most bothersome side effects. DMPA is a prescription drug and a visit to the clinician is necessary every 3 months. The delay in fertility (averaging up to 12 months) may not make DMPA an option if pregnancy is desired sooner.