Injectable

The progestin-only contraceptive injection (or 'depo injection') contains a synthetic version of the natural hormone progesterone.

The injection primarily prevents ovulation and also thickens the cervical mucus, making it harder for the man’s sperm to pass into the uterus.

Typically the injection is given intra-muscularly into the buttock but the deltoid or thigh can also be used.

A newer version of a progestin injection can be given subcutaneously i.e. into the skin.

The injection procedure is quick, straightforward and generally pain-free, and has to be repeated on a regular basis depending on the product.

The injection works within 7 days of being given.

Common products

• Depot medroxyprogesterone acetate (DMPA, also called “depo injection,” “the jab,” the injection, Depo, Depo-Provera, Megestron, and Petogen. The new subcutaneous version is called DMPA-SC), given every 3 months
• Norethisterone enanthate (NET-EN, also called Noristerat, and Syngestal), given every 2 months

How effective is the depo injection at preventing a pregnancy?

Progestin only contraceptive injections are very effective contraceptives, although their long term effectiveness very much relies on the woman returning on time for her next injection.

Assuming a woman returns on time for her injection then they are 99% effective at preventing a pregnancy.

Evidence suggests that real-world use, where some women do forget to return on time, reduces the effectiveness to around 97%.

What are other good things about depo injections?

They are safe and suitable for nearly all women.

Some reasons that a woman might not be suitable include: if she is breast feeding a child less than 6 weeks old; if she has abnormal vaginal bleeding; if she has or had breast cancer; a history of or current deep vein thrombosis; severe liver disease; high blood pressure; or long standing diabetes and any cardiovascular disease.

What women say they like about the depo injection

According to the WHO, some women prefer the injection because: they do not have to think about taking something every day; it does not interrupt sex; it temporarily stops their periods; and it helps some women put on weight.

What aspects of the injection might women not like/ should they be aware of?

Progestin-only injections can cause side effects.

Common side effects include changes in the bleeding pattern (from irregular to complete absence) weight gain, headaches and dizziness.

In some women it may take a couple more months for their fertility to return once they decide to stop the injections.

Counselling should make women aware that this method may delay their return to fertility.

Unlike condoms, progestin-only injections do not protect against sexually transmitted infections.