Predictors of low risk of persistent trophoblastic disease in molar pregnancies.

OBJECTIVE

To search for predictive factors for low risk of persistent trophoblastic disease in patients with molar pregnancies.

METHODS

A total of 270 consecutively collected, histologically confirmed hydatidiform moles were classified by ploidy using karyotyping and flow cytometry. The parental origin of the genome was determined by analysis of microsatellite polymorphisms. Data on clinical features and pathology reports were collected for each patient.

RESULTS

The observed frequency of persistent trophoblastic disease in patients with triploid moles was 0 of 105, (95% confidence interval 0-2.8%), whereas 28 of 162 patients with diploid molar pregnancies developed persistent trophoblastic disease (P < .001). Patients with a diploid mole and an initial hCG level lower than 49,000 units per liter did not develop persistent trophoblastic disease (P = .03).

CONCLUSION

The risk of persistent trophoblastic disease after a triploid mole is very low. By combining the present data with data from published studies with valid ploidy assessment, the frequency of persistent trophoblastic disease in patients with triploid moles is 0 of 196 (95% confidence interval 0-1.5%). We suggest that the surveillance program for patients with triploid molar pregnancies is shortened. Initial hCG less than 49,000 units per liter is a possible predictor of low risk of persistent trophoblastic disease in women with diploid molar pregnancies, but this observation needs confirmation in larger studies.