Objective To analyze temporal trends of hospital admissions due to molar pregnancies in Italian and non-Italian women in Lombardy during the 1996–2008 period.

Methods A standard form is used to register all discharges from public or private hospitals in Lombardy. Hydatidiform mole (HM) cases were identified when searching the database for code 630 of the International Classification of Diseases, Ninth Revision (ICD-9). Ratios of HM per 100,000 pregnancies in strata of age and nationality were computed.

Results The estimated frequency of HM in Lombardy over the period 1996–2008 was 104.4 per 100,000 pregnancies (SE, 2.8) or 1 case in 935 pregnancies. The frequency of HM tended to decrease in the late 1990s, the crude ratio per 100,000 pregnancies being 127.3 in 1996, 89.3 in 2000, and 113.1 in 2008. The temporal trend analysis, adjusted for age class and geographical origin, showed a significant decrease (P = 0.025). The frequency of HM was 99.8/100,000 pregnancies among Italian women, 112.1/100,000 pregnancies among women from other European countries, 85.1/100,000 pregnancies among women from Africa, 176.9/100,000 pregnancies from South America, and 163.0/100,000 pregnancies among Asian women. Considering the periods 1996–2001 and 2002–2008 separately, the frequency of HMs was largely similar for all groups, except in Asian women: in this group, the frequency of HMs was 242.7/100,000 pregnancies and 120.1/100,000 pregnancies in 1996–2001 and 2002–2008, respectively.

Conclusion Between 1996 and 2008, the HM incidence in Lombardy showed a slight but significant decrease, mostly owing to the decrease of HM incidence among Asian women.