Many women (pregnant or not) experience spotting after routine Pap smears. This doesn't mean anything is necessarily wrong with your pregnancy. In fact, pregnant women are more likely to have spotting after a Pap test, since your uterus, vagina, and surrounding tissues are more engorged with blood. However, if the bleeding becomes heavy or lasts longer than a few hours, give your doctor a call.
For the same reasons you've probably had Pap smears before getting pregnant, it's important to continue getting them while you're expecting. The test looks for changes to cells in the cervix (the lower end of your uterus) that could lead to cervical cancer if left untreated. A Pap is a routine part of ob-gyn visits, and you'll probably have one at your first prenatal appointment.