Protected sex and delayed period?

Patient: I had protected sex with my girlfriend last Sunday through Tuesday. We did it 4 times, with me ejaculating each time. Afterwards, I checked the condoms to make sure they weren’t broken, and they seemed to be fine. She was supposed to have her period last Wednesday, but still hasn’t gotten it 6 days since. She says she is very regular with her period cycles. Polycystic ovary syndrome runs in her family. What’s going on with her? Could she be pregnant? Can sex this close to the beginning of a period delay it?