What Is The Contraceptive Injection?

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With so many choices of birth control available, it can be a difficult task to decide on the best choice for you. No single method of contraception is suitable for everyone as each type of birth control has its pros and cons. With the help of your healthcare professional, your choices can be narrowed down based on your medical background, lifestyle, and any family planning goals you might have.

The contraceptive injection is a long-acting reversible contraceptive. It may be a good choice if you cannot use oestrogen-based contraception. It lasts for 8 or 13 weeks, depending on the type of injection, and is not affected by other medicines. In some women, it helps to reduce heavy, painful periods and can also ease premenstrual symptoms.

The injection, however, might not be the right choice if are planning to fall pregnant as it can take up to 1 year for your fertility to return to normal after the injection wears off.

How Does The Injection Work?

The contraceptive injection prevents pregnancy by injecting a synthetic version of the hormone progestogen, called Depot medroxyprogesterone acetate, or DMPA. The injection is also commonly known as Depo. Depo prevents the body from producing its own hormones and releasing eggs from the ovaries.

The contraceptive injection steadily releases the hormone progestogen into your bloodstream, which prevents the release of an egg each month (ovulation). It also thickens the cervical mucous which makes it difficult for sperm to move through the cervix and into the uterus (womb) where it could fertilise an egg. Because Depo thins the lining of the uterus it is less likely for a fertilised egg to implant itself.

Depo-Provera is the most administered injection in the UK and lasts for 13 weeks. Other brands that might occasionally be used include Noristerat, which lasts for 8 weeks and Sayana Press, which also lasts for 13 weeks, but is not yet widely available.

Who Should Not Have The Injection?

Deciding which contraceptive method is right can be difficult as there are many methods available to help prevent pregnancy. Issues to consider when choosing the most suitable birth control method include medical history, sexual lifestyle, costs, future pregnancy plans and side effects. Although the injection is a very effective and long-lasting contraceptive, it is not suitable for all women.

The contraceptive injection may not be suitable for you if:

  • you are pregnant (or unsure if you are pregnant)
  • you do not want your menstrual cycles (periods) to change
  • you want to have a baby in the next year
  • you have unexplained bleeding in between periods or after sex
  • you have arterial disease or a history of heart disease or stroke
  • you have liver disease
  • you have or had breast cancer 
  • you are at risk of osteoporosis

How Is The Injection Given?

It is important to be certain that you are not pregnant when you have your first injection. You should do a pregnancy test to confirm your status if you are sexually active.

The Depo-Provera and Noristerat injections are given into a muscle, usually in your bottom or sometimes in your upper arm. The Sayana Press injection is given into your abdomen (tummy) or thigh. 

When Should You Have The Injection?

You can have the injection at any time during your menstrual cycle but should not be pregnant. If you have the injection during the first 5 days of your menstrual cycle, you will have immediate protection against becoming pregnant. If you have the injection after the first 5 days of your cycle, you will need to use extra protection, such as condoms, for 7 days.

After Giving Birth

You can have the injection any time after giving birth unless you are breastfeeding, in which case the injection will be given after 6 weeks. The contraceptive injection is safe to use while breastfeeding.

If you are given the injection within 21 days of giving birth, you will be immediately protected against becoming pregnant. If you have the injection more than 21 days after giving birth, you will need to use additional protection, such as condoms, for 7 days.

You may experience heavy and irregular bleeding if you have the injection within the first few weeks of giving birth.

After A Miscarriage Or Abortion

You can have the injection immediately after a miscarriage or an abortion and will have immediate protection against pregnancy. If you are given the injection more than 5 days after a miscarriage or abortion, you will need to use condoms for 7 days.

What Are The Benefits Of The Injection?

Although the contraceptive injection might not be as convenient as other hormone-based contraceptive methods, such as implants or IUDs, that last up to 7 years, the injection still provides many benefits:

  • When used correctly, it is more than 99% effective.
  • Because it lasts for 8 or 13 weeks (depending on which injection you have) you do not have to worry about remembering to take daily or weekly contraceptives or needing to interrupt sex when using a barrier method such as condoms.
  • It can be used by women who cannot use contraception that contains oestrogen.
  • It is not affected by other medicines or herbal products that may lower the levels of progestin in your blood. Medicines known to do this include certain seizure medicines, sedatives, HIV medicines and the herb St. John's wort.
  • Your periods may become shorter, lighter or stop altogether. 

What Are The Disadvantages Of The Injection?

Like any form of contraception, the injection has its drawbacks and potential risks. These include the need to remember when to get the next shot to prevent it from expiring or losing effectiveness. Side effects such as weight gain, mood swings, headaches, breast tenderness, and irregular bleeding can occur. Depo-Provera, the specific injection mentioned, impacts natural estrogen levels, potentially leading to bone thinning. Menstrual cycles may become more erratic or heavier. Additionally, if planning to conceive, the injection may not be the optimal choice as it can take up to a year for fertility to return to normal after its effects wear off. It is important to note that despite using the injection, protection against sexually transmitted infections (STIs) remains necessary, often requiring the use of condoms.

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