Gestation Calculator

This calculator has been designed to give you an idea of the treatment options available to you*. If you decide to have an abortion with Marie Stopes UK, one of our nurses will give a more approximate gestation date during your appointment by way of a scan.
*Please note that this online calculator will only give you an estimated gestation based on the details you have provided.

Please select the first day of your last menstrual period.



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The contraceptive injection (Depo-Provera)

The contraceptive injection, or Depo-Provera, is an injection usually given in your buttock. It contains the hormone progesterone which stops ovulation (release of an egg) and also thickens the mucus around the cervix, which makes it difficult for sperm to get into the uterus.

The injection is a long-acting reversible contraceptive (or LARC). These types of contraception are recommended by Marie Stopes United Kingdom, as they are over 99% effective - they’ve been shown to be 20 times more effective than short-term contraceptive methods such as the pill, patch or vaginal ring.

Long-acting methods of contraception all have the advantage that once in place, you don’t need to think about them until they need replacing. None of them interrupt sex. 

Injection advantages 

  • It lasts for 12 weeks.
  • It can help with heavy periods.

Things to consider

  • Unlike condoms, the contraceptive injection does not protect from sexually transmitted infections.
  • Some women may find they have spotting and bleeding for the first few weeks, but this usually settles down.
  • Other common side effects include headaches, spotty skin and a small amount of weight gain.
  • Evidence suggests that the injection decreases bone density, but there is no increased risk of fracture. Guidelines recommend you re-evaluate if this is the best method for you with a healthcare professional every two years.
  • Periods may stop completely after 3-6 months, which is normal.
  • Fertility may take several months to return after stopping the injection.
  • As it is an injection, if you have any symptoms (bleeding etc), you cannot reverse this method immediately. 

Injection aftercare advice

If you have your first injection on day 1 to 5 of a period, it will work straight away. At any other time, extra precautions such as condoms or abstaining from sex will be required for seven days. 

You can have an injection following Marie Stopes UK abortion treatment. It will be given to you during your treatment and will work straight away. It will then last a further 12 weeks before another injection is required.


Available download:

PDF icon LARC leaflet.pdf1.69 MB