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Unwanted 72 is an emergency contraceptive pill containing high amount of progesterone. These medicines have a severe side effect of heavy or irregular bleeding. Your wife had the same side effect.
Please check her hemoglobin levels; she might turn anemic if she bleeds much. Continue taking iron pills. It might take one or two cycles to get her periods to get regular again.
So, preferably maintain a regular regime with condoms or oral contraceptive pills like Novelon, Ovral L, etc., rather than an emergency contraceptive. They are way safer.