A direct way of contracting this cancer is a smoker has a higher chance of cervical intraepithelial neoplasia (CIN3) occurring, which has the potential of forming cervical cancer. When CIN3 lesions lead to cancer, most of them have the assistance of the HPV virus, but that is not always the case, which is why it can be considered a direct link to cervical cancer. Heavy smoking and long-term smoking seem to have more of a risk of getting the CIN3 lesions than lighter smoking or not smoking at all. Although smoking has been linked to cervical cancer, it aids in the development of HPV, which is the leading cause of this type of cancer. Also, not only does it aid in the development of HPV, but also if the woman is already HPV-positive, she is at an even greater likelihood of contracting cervical cancer. Long-term use of oral contraceptives is associated with increased risk of cervical cancer. Women who have used oral contraceptives for 5 to 9 years have about three times the incidence of invasive cancer, and those who used them for 10 years or longer have about four times the risk. Having many pregnancies is associated with an increased risk of cervical cancer. Among HPV-infected women, those who have had seven or more full-term pregnancies have around four times the risk of cancer compared with women with no pregnancies, and two to three times the risk of women who have had one or two full-term pregnancies. The Pap test can be used as a screening test, but produces a false negative in up to 50% of cases of cervical cancer. Other concerns is the cost of doing Pap tests, which make them unaffordable in many areas of the world. Confirmation of the diagnosis of cervical cancer or precancer requires a biopsy of the cervix. This is often done through colposcopy, a magnified visual inspection of the cervix aided by using a dilute acetic acid (e.g. vinegar) solution to highlight abnormal cells on the surface of the cervix, with visual contrast provided by staining the normal tissues a mahogany brown with Lugol's iodine. Medical devices used for biopsy of the cervix include punch forceps. Colposcopic impression, the estimate of disease severity based on the visual inspection, forms part of the diagnosis. Further diagnostic and treatment procedures are loop electrical excision procedure and cervical conization, in which the inner lining of the cervix is removed to be examined pathologically. These are carried out if the biopsy confirms severe cervical intraepithelial neoplasia.