Why no intercourse?

Janna • Mom to angel twins born sleeping at 18w and a chemical baby. RIP Maven and Macie and Littlefoot.
I've been thinking about this.. The doctor told me not to have any intercourse until the bleeding stopped because my cervix is open and there is a higher risk of infection. But, isn't your cervix open during your monthly cycle as well? So why would I be at more of a risk of infection now than any other time the cervix is open?