Is it sufficient to have cervical smear every 3 years?

Abnormal cervical cells usually take around 5 to 10 years to develop into cancer. Therefore, screening at 3-yearly interval is frequent enough to pick up changes before they become serious. The International Agency for Cancer Investigation obtained data from cervical programme in developed countries and found that the benefits of annual screening over 3-yearly screening are negligible, but the costs are considerably higher. On the other hand, screening at interval longer than 3 years is not effective enough to prevent cervical cancer.