Oral contraceptives and risk of gestational trophoblastic disease

Clinical reports suggested that the use of oral contraceptives (OC) after a molar pregnancy may increase the risk of persistent throphoblastic disease. However, few epidemiologic studies have analyzed the effect of OC use on the risk of developing gestational trophoblastic disease (GTD). To give further information, we have analyzed data from a case-control study on risk factors for GTD. Cases were 268 women with a histologically confirmed diagnosis of complete or partial mole referred to the participating Trophoblastic Disease Centers. A total of 268 subjects were interviewed; 79 cases were classified as partial and 159 as complete mole. Controls were randomly selected women who gave birth to healthy infants at term on randomly selected days in the same network of hospitals in which cases had been identified. A total of 104 cases and 130 controls reported ever OC use, and the corresponding odds ratio (OR) was 1.5 (95% CI, 1.1-2.1). The risk of GTD increases with duration of OC use: the OR was 1.7 (95% CI 1.2-2.6) for ever-users reporting >or=12 months of use. No consistent pattern of risk was observed with time since last OC use. We have analyzed separately the association between OC use and risk of complete and partial moles: no statistically significant difference emerged, but the OR for partial moles was higher (OR 3.0, 95% CI 1.6-8.4) than for complete mole (OR 1.0, 95% CI 1.8). In conclusion, we observed a weak association between OC use and GTD; such a weak association could be explained by factors other than causality.