Depo Provera, commonly called “Depo” or “the shot,” is a very effective method of birth control. It is an injection of a synthetic (human-made) hormone that is given once every 12 weeks by a health care provider.
How Effective is It?
Depo is over 99% effective in preventing pregnancy. (Less than 1 pregnancy per 100 women per year.)
How Does It Work?
When Depo is in the bloodstream it prevents the ovaries from releasing an egg each month. In other words, it prevents ovulation. If no egg is released, you will not get pregnant. Depo thins the lining of the uterus, which prevents implantation of a fertilized egg. It also thickens cervical mucus to make it more difficult for sperm to pass through her cervix.
Are There Side Effects?
Like any other hormonal birth control method, some experience side effects.
You should expect irregular bleeding on Depo. Some people have longer periods, some have bleeding in between periods, and some stop having any periods at all. None of these patterns are dangerous or suggest that Depo is not effective as a method of birth control.