Subsequent pregnancies after a diagnosis of pregnancy-associated cancer

Introduction: Pregnancy-associated cancer is a rare but clinically significant event. Decisions regarding subsequent pregnancies after such a diagnosis are complex and influenced by medical, psychological, and social factors. This study aimed to investigate the probability of having a subsequent pregnancy following a diagnosis of a pregnancy-associated cancer. Material and Methods: We conducted a record-linkage cohort study using the regional health databases of Lombardy, including the hospital discharge records and the certificate of delivery assistance. Pregnancies were deliveries and abortions occurring between 1 January 2007 and 31 December 2017. Pregnancy-associated cancer was defined as any malignant neoplasm first diagnosed during pregnancy or within 1 year after the end of pregnancy, identified through hospital admissions carrying a new cancer diagnosis. To ascertain subsequent pregnancies after a diagnosis of pregnancy-associated cancer, we tracked deliveries and abortions through 31 December 2023. We estimated the incidence of pregnancy-associated cancer per 1000 pregnancies with the corresponding 95% confidence intervals (CIs) and calculated the cumulative probability of a post-diagnosis pregnancy using the cumulative incidence function that accounts for the competing risk of death. Results: A total of 832 incident pregnancy-associated cancers were recorded among deliveries and 325 among abortions, corresponding to incidence rates of 1.12 per 1000 deliveries (95% CI, 1.04–1.19) and 1.27 per 1000 abortions (95% CI, 1.13–1.41). Breast cancer was the most frequent diagnosis in both groups (31% among deliveries, 40% among abortions), followed by thyroid cancer; the third most common site was lymphoma among deliveries and cervical cancer among abortions. During follow-up, 77 women had a subsequent pregnancy (59 deliveries, 18 abortions), yielding a cumulative probability of 7.3%. Stratified by age at diagnosis, women under 35 had a substantially higher probability of subsequent pregnancy compared to women aged 35 or older (14.0% vs. 3.5%, p < 0.01). Furthermore, the cumulative probability of subsequent pregnancy was lower among women treated with antineoplastic therapy than among those who were not treated (4.3% vs. 10.1%, p < 0.01). Conclusions: Subsequent pregnancies following a pregnancy-associated cancer diagnosis were relatively uncommon, highlighting the need for integrated reproductive counseling within a multidisciplinary approach.