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 patch (Evra)

The contraceptive or combined patch is a thin, sticky patch that is applied to clean, dry skin. A new patch is used every 7 days for 21 days, followed by 7 days without a patch. In the UK, its brand name is Evra.

How does the contraceptive patch work?

The patch works by releasing the hormones oestrogen and progestogen. It is applied once a week for 3 weeks each month. When in place, the released hormones prevent the ovaries from releasing an egg each month (ovulation), thicken cervical mucus (so that it is harder for sperm to move into the womb) and thin the lining of the womb.

Typical use failure rate is up to 9%. (Up to 9 women in 100 will have an unplanned pregnancy in the first year of use.)

Contraceptive patch advantages

  • You don't have to think about contraception every day, like with the pill.
  • It can make periods regular, lighter and less painful.
  • It is not affected by vomiting or diarrhoea.

How to use the contraceptive patch

  • Apply a patch to the skin of your abdomen, buttock, arm, shoulder or top of your leg - but avoid your breasts. The patch will work straight away.
  • Wear this patch for 7 days and then change for a new one.
  • After another 7 days, change it again for a third patch (the patch change day every week should be the same).
  • After you have worn 3 patches for 7 days each, have a 7 day break, during which time you should have a period-like bleed.
  • After the 7 day break start a new patch cycle.
  • Find out what to do if your patch falls off.

Things to consider about using the patch

  • It can be seen on the skin.
  • It can occasionally cause skin irritation.
  • It may fall off within the 7 days.
  • It is not suitable for women with high blood pressure.
  • It is not suitable for women over 35 who smoke.
  • It may not be suitable for women who have migraines.
  • Taking some other medications can make it less effective.
  • Side effects include mood swings, breast tenderness, and headaches.
  • There's a small risk of blood clots.
  • Unlike condoms, the patch offers no protection against sexually transmitted infections.