Among HPV-positive women, any use of oral contra­ceptives was associated with a significant increase in risk of cervical carcinogenesis (OR = 1.47); use for less than 5 years was not related to the development of cervical cancer (OR = 0.77), but the risk increased significantly for 5-9 years of use (OR = 2.72) and for 10 or more years of use (OR = 4.48) [13]. A recent meta-analysis confirmed the interaction between the use of oral contraceptives and HPV infection in the risk of cervical cancer, particularly for prolonged periods [14]. These findings strongly suggest either that steroid hormones interact with HPV in the cer­vical carcinogenesis or that women using oral contracep­tives are more prone to hazardous sexual activity that leads to HPV infection.

High parity is a risk factor for cervical cancer. Human papillomavirus-positive women who reported seven or more full-term pregnancies had a 4-fold increased risk of cervical cancer as compared to similar HPV-positive women who were nulliparous (OR = 3.8) [8].

Smoking was associated with a 2-fold statistically significant increased risk of cervical cancer with a signifi­cant dose response, and is an independent risk factor for cervical cancer [15].

Some sexually transmitted infections (herpes simplex virus type 2, human immunodeficiency virus and non spe­cific infection) have repeatedly been found to be associ­ated with cervical cancer [8]. Thus, there is a 2-fold in­creased risk for the presence of antibodies to Chlamydia trachomatis (OR = 2.1) [8]. Other environmental risk factors, such as socioeconomic status and nutritional fac­tors that are in favor of the spread and the maintenance of sexually transmitted infections, are under evaluation [1].

Although studies in males are rarer, there is consistent evidence that circumcision protects against persistent HPV infection and subsequent cervical cancer development in partners [16]. Furthermore, even though condom use does not protect against all HPV infections, it does promote regression of CIN and clearance of HPV infection [17].