Long-term use of oral contraceptives and cervical neoplasia: an association confounded by other risk factors?

One-hundred-and-forty women with cervical intraepithelial neoplasia (CIN) found during pregnancy were compared to 280 pregnant age-matched controls. Information was obtained on obstetrical and gynecological history, sexual behaviour, contraceptive use and smoking of the female and of the male partner. Oral contraceptive use for 60 months or more was significantly associated with CIN. This significance vanished when the effect of confounding factors was controlled for in a log-linear analysis. According to these results, long-term oral contraceptive use does not seem to be a causal factor of CIN, but these women constitute a high risk group due to sexual history and smoking habits and should thus be referred for a regular cytological screening.