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they may not be very effective in the first month itself. 6 I would advise you to follow Another contraceptive method like barrier method , condom is , during the first month.Take the pill regularly and it will be very effective from the second month.
However there are chances of failure of contraception
while on oral contraceptive pills
. But the chances are very very low. You should also keep in mind your safe period and fertile period to achieve hundred percent contraception.