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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I can’t feel my IUD/IUS strings

If you can’t feel your IUD strings you need to use another contraceptive method or not have sex until the presence of the IUD or IUS can be confirmed.

If your additional contraceptive method fails, remember you can still take the emergency contraceptive pill.

 checking IUS Mirena threads hormonal coil

See your GP or family planning clinic as soon as possible. A health professional will do a gentle examination to see if the threads are present. If not, they may try to retrieve them using a thread retrieving device. If thread retrieval is unsuccessful, a scan will be arranged.

Remember that you can stop an unintended pregnancy by using emergency contraception methods such as the emergency pill or ‘morning after pill’. The progesterone-only pill is a hormone pill and works by delaying the release of an egg from an ovary, therefore preventing pregnancy. It can be taken up to 120 hours (5 days) after unprotected sex. Efficacy varies, depending on when in your cycle the sex happened, however, the IUD is more effective at preventing pregnancy.

Emergency contraception is more effective the quicker you act, so if you’ve had unprotected sex, you should visit a Marie Stopes United Kingdom clinic, your GP or local sexual health centre as soon as possible.

If you want to find out whether you are pregnant, a pregnancy test will not be accurate until 2-3 weeks after the sex happened. It's advisable to take a pregnancy test after using the emergency contraceptive pill, as failure is quite common.

You should only use emergency contraception in an emergency and not as a regular form of contraception.

Please note that as well as pregnancy, following unprotected sex you could be at risk of sexually transmitted infections (STIs) such as chlamydia and should visit your local genito-urinary medicine clinic (GUM clinic) or Marie Stopes London STI clinic for testing.