Hormonal Methods of Contraception: Contraceptive Injections and IUDs

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  • 0:01 Contraception
  • 2:06 Depo-Provera Injection
  • 5:57 IUDs
  • 10:24 Lesson Summary
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Lesson Transcript
Instructor: Heather Adewale

Heather has taught reproductive biology and has researched neuro, repro and endocrinology. She has a PhD in Zoology/Biology.

Did you know there are some methods of birth control that last up to five years! Or, if that is too long, some that last three months at a time? Learn about these two options in this lesson on contraceptive injections and IUDs.


So, we all know about the birds and the bees; I'm sure many of you had that somewhat awkward talk with your parents or in health class. And, hopefully, that talk included something about birth control. Or, perhaps you've been to your doctor lately, and they've asked you, 'what methods of birth control do you use?' Or, maybe they used a less familiar term, contraceptives.

See, what many commonly call birth control, often referring to things like condoms and birth control pills, is also called contraception or contraceptive methods. Contraceptives are methods that can be used to manage fertility or prevent conception (or fertilization), the fusion of the female's egg with the male's sperm. See, the prefix 'contra-' means against or opposite, so 'contra'ception is against conception, making its goal to prevent the sperm from meeting the egg, thus preventing conception!

The doctor may have also explained there are different types of contraceptives and that some of these use hormones. These are called hormonal forms of contraception. They accomplish the goal of contraception by altering the levels of the female hormones estrogen and progesterone to prevent fertilization and pregnancy. These can come in the forms of pills, patches saturated with the hormones, implants and other methods that allow the hormones to enter the body.

But, for some women, having to remember to take a pill every day, or change a skin patch once a week, or even getting an implant put under the skin is too much to worry about. That's where the option of getting a hormone injection may come in handy! It's quick, convenient and, once done, you don't have to think about it for another 12 weeks.

Depo-Provera Injection

The most common hormone injection used for contraception in the United States is called Depo-Provera. It's a progesterone-based injection, given in the arm or buttocks, that provides contraception for 12 weeks at a time. You can think of it like it's depositing progesterone into the body. The progesterone enters the bloodstream where one of its jobs is to fool the body into thinking it's already pregnant.

When you're pregnant, the ovaries start producing higher levels of natural progesterone to let the brain and the rest of the reproductive system know that 'a baby is on the way, so halt the production of more eggs and get ready!' By injecting the body with man-made (or synthetic) progesterone, we're trying to imitate or mimic this process. Our synthetic progesterone looks similar to natural progesterone, kind of like it's wearing a mask to help fool the body into thinking it's the real thing.

So, how exactly does it work? Well, the progesterone-only forms of contraceptives use a few different methods to achieve contraception:

  • They prevent ovulation, or the release of a mature egg from the female's ovary.
  • Thicken the mucus in the cervix, the area circled below, to prevent sperm from passing through and into the uterus. This helps prevent fertilization because the sperm cannot reach the egg.
  • They thin the lining of the uterus, making it more difficult for a fertilized egg to attach to it.

The cervix is circled in yellow.
imagine with cervix circled

And, of course, like all hormonal forms of birth control, the Depo injections have both advantages and disadvantages. Let's start with the good! Advantages:

  • First, as you've already learned, it's convenient - one injection every three months!
  • It also doesn't interfere with sex or daily activities.
  • It has less side effects than estrogen/progesterone combination pills.
  • It can be used by nursing mothers.
  • It even has some health benefits, including a reduction in pain and bleeding for those suffering from certain conditions of the reproductive tract, such as endometriosis or uterine fibroids.

But, of course, these come alongside some potential disadvantages. Depo injections, like other forms of hormonal contraception, do not provide protection against STDs. In addition to many common side-effects of hormonal contraceptives, such as headaches, nausea and breast tenderness, Depo-Provera can also cause:

  • Slight weight gain
  • Irregular menstrual bleeding or spotting
  • Possible bone loss (however, this is reversed once injections are stopped)
  • An increased risk of blood clots and cardiovascular disease, especially in women who smoke or have a history of cardiovascular disease or circulatory problems

Women on Depo injections also take longer to return to normal fertility than other methods of contraception - around 10-12 months after the injections have stopped. And, of course, our patient just has to make sure she schedules an appointment for her next injection every 12-13 weeks to keep the progesterone levels in her body consistent. If this schedule is followed, Depo-Provera injections are 99.7% effective in preventing pregnancy; however, the average failure rate during the first year is closer to three percent.


But, maybe the thought of a needle every few months is too much for our patient, or maybe she wants something she can forget about for a few years - then an intrauterine device (IUD) might be the right choice. This small, plastic, T-shaped device is placed inside the uterus just like the name 'intra-uterine' suggests, and is left there for up to five or ten years. It has small strings that hang outside the cervix that allow the doctor to check the IUD and help in its removal from the uterus. But don't worry, while it may sound a little uncomfortable, most women only experience slight discomfort for the first few days and then don't even notice it's there.

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