Final answer:
According to ACOG guidelines, women should have their first Pap smear at age 21 if they are sexually active. Routine screening should continue until age 65.
Step-by-step explanation:
According to the American College of Obstetricians and Gynecologists (ACOG) guidelines, women should have their first Pap smear at age 21 years if they are sexually active. Routine Pap smears are recommended every three years until age 50, and then every five years until age 65, if the previous tests were normal. It is important to note that screening may be discontinued after age 65 if the last three Pap smears were normal or if a person has had a complete hysterectomy and no longer has a cervix.