How effective are morning after pills?

Hi,
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Morning after pills or emergency contraceptives pills are effective in preventing pregnancy if taken within 48-72 hour of unprotected intercourse. The chances of pregnancy cannot be ruled out since you were close to your probable ovulation time at the time of intercourse. If you have not had further unprotected intercourse after taking emergency contraceptive, then you will continue to have protection against pregnancy (that could have resulted from the last intercourse). The stomach cramps that you have could be due to probable withdrawal bleeding that might start any time (as a result of high hormonal content in emergency contraceptive that result in bleeding about 5-7 days of taking the pills). Wait and watch for your periods. If you intend to be sexually active consider getting started on suitable regular birth control when you have your periods.
Take care.