Objectives The aims of this study were to estimate the occurrence of pregnancy-associated cancer overall and by site, to evaluate if the risk increases over time, and to investigate some major determinants.

Methods This is a population-based linkage study using the regional hospital discharge forms [Scheda di Dimissione Ospedaliera (SDO)] database of Lombardy, Italy, a region with 10 million inhabitants. All resident women with a SDO reporting a birth or abortion between 2001 and 2012 were identified. Pregnancy-associated cancers were defined as a cancer occurring during pregnancy or within 12 months after pregnancy and were identified by selecting all SDOs reporting a first diagnosis of cancer. Risk of developing a pregnancy-related cancer was calculated as the ratio of the number of pregnancy-related cancers to the total number of pregnancies. The effect of potential predictors on the risk was estimated using a logistic regression model, and odds ratios (OR) were estimated.

Results During the period 2001–2012, the risk of pregnancy-related cancer was 122.9 per 100,000 pregnancies. The most common cancers were breast cancer (479 cases, 39.9/100,000 pregnancies), thyroid cancer (186 cases, 15.5/100,000), and lymphomas (157 cases, 13.1/100,000). Skin cancer accounted for 177 cases (14.8/100,000), half of which were melanomas. The risk of developing a pregnancy-related cancer increased significantly with age, from 60 of 100,000 for women less than 30 years old to 265 of 100,000 for women aged more than 40 years. Italian women had a higher risk than foreign ones (OR, 1.6), and the pregnancy outcome was more frequently an abortion (OR, 1.2), whereas no trend in risk was observed with calendar year (P = 0.249).

Conclusions This study confirms previously reported incidence estimates but does not show increases over time.