Having intercourse without a condom the night before a Pap will not make a normal Pap smear abnormal, but it might obscure cervical cells so that it cannot be accurately read.
Should you cancel if you “forgot” the night before? Realistically, after waiting two months for an appointment, asking for the afternoon off work or desperately needing a refill on your birth control pills, it may not be practical to take a pass. Be sure to mention to your gynecologist that you had sex, and be aware that you may get a call back if the Pap can’t be read accurately.
On the other hand, if you are coming in specifically to check out an abnormal discharge or odor, you should probably reschedule. It’s pretty much impossible to figure out what is going on if you had intercourse hours before your visit.
If you are coming in for another problem, say abnormal bleeding, an STD check or pelvic pain, it really doesn’t matter.
Is it ever a good thing to have sex before your appointment? Actually, yes. If someone tells me they bleed every time they have sex, it is helpful to see where it is coming from -- the uterus, cervix or vagina.