<s>[INST] My girlfriend took an i-pill after 18 hours of unprotected sex. I didn't ejaculate inside her but still she took the pill for preventive measures. Her periods were due to start 7-9 days after sex. She got her period but it lasted for only 2 days. As well as the bleeding was very light comparing to her normal periods.Can consuming an i-pill for the first time cause irregularity in periods? What can be the effects of it on periods? Can the bleeding in the periods after taking the pill be relatively light? [/INST] hi thanks for your queryyes consuming an i- pill any time can cause irregularity in cycle.most of the time it causes delay in periods.usually does not affect the amount of bleeding . first rule out pregnancy by urine pregnancy test if no pregnancy then tell her to keep menstrual chart and use a good contraceptivealso .if again decreased flow then she needs hormonal evaluation .as decrease in flow could be due to others reasons as thyroid disorder ,hyperprolactinemia wt loss ,stress, </s>