Frequency of hydatidiform mole in Lombardy, Northern Italy

The frequency of hydatidiform mole in Lombardy (a region in Northern Italy with 8.9 million inhabitants) over the period 1979-1982 was estimated using the Regional Hospital Discharge Registration System, where information is collected on all discharges from public and private hospitals. After revision of registrations and clinical records, 347 cases of hydatidiform mole were confirmed. The estimated frequency was 66.22 per 100,000 pregnancies (SE = 3.56), or 1 in 1510 pregnancies. The risk of hydatidiform mole was not elevated in teenage women, but rose markedly above age 40, and was almost 300 times higher for women age 50 or older. The frequency of hydatidiform mole observed in the nine provinces of Lombardy was significantly heterogeneous, and this variation could not be explained in terms of differences in maternal age distribution.