Hallow Dear, I-pill is Plan B emergency post coital pill which can effectively prevent the pregnancy if taken within 72 hours of unprotected sex. Your girlfriend has consumed these pills within 3-4 hours of the unprotected sex. So the chances of pregnancy due to this unprotected sex are very remote. I-pill contains Levonorgestrel which is a progestational medicine. Hence after its consumption, it may cause very little withdrawal bleeding after few days. Moreover, it may delay the following period by few days to a week or so. You may consider her delay in the period as a side effect of I-pill. She would get her menses within a weeks time or so. If still she does not get the menses after one week, you may confirm the pregnancy status by pregnancy test overnight first morning urine sample. I hope this helps you. Dr. Nishikant Shrotri