Risk of Pregnancy

What is my risk of getting pregnant if I have sex without using contraception or my birth control fails?

Almost any time you have sex without using birth control effectively,
there’s a chance you might get pregnant – and using emergency
contraceptive pills (also called "morning
after pills" or "day after pills") can significantly
reduce your risk.
Your chances of getting pregnant if you have unprotected sex and don’t
use emergency contraception
afterwards vary, depending on where you are in your monthly cycle.
Researchers have calculated the average risk at different times in
a woman’s monthly cycle, but it’s important to remember
that your risk could be higher or lower. The risk is highest on the
days right before you ovulate (when your ovaries release the egg),
reaching a maximum of nearly 30%. You can’t know for sure when
you will ovulate, so researchers have calculated the average risk
of pregnancy based on a woman’s monthly cycle (since you can
figure out when you started your last period).

During the first two days of a woman’s cycle (day 1 being your
first day of bleeding), the average risk of pregnancy is virtually
zero. After the first two days, the risk starts to rise steadily,
reaching 9% on or about day 13. Then it begins to decline slowly until
it levels off at about 1% on day 25. It stays at about 1% for the
rest of your cycle. (The average monthly cycle lasts 29 days, but
it is perfectly normal to have a cycle that lasts as little as 20
days or less or as long as 40 days or more.)

Emergency contraception works before ovulation, but does not appear to work after ovulation has already occurred. ella works closer to the time of ovulation than progestin-only pills, like Plan B One-Step or Next Choice One Dose. Therefore, if you believe that you have had unprotected sex close to the time of ovulation, it might be best to use ella if possible. But it can take time to get a prescription and fill it – the most important thing is to take action as soon as possible after unprotected sex.

If you’ve had unprotected sex and are wondering if you at risk of pregnancy, this tool from Planned Parenthood can help.

A thorough and up-to-date academic review of the medical and social
science literature on emergency contraception, including how it reduces
the risk of pregnancy after sex, is available
here .