Spontaneous and induced abortions in women with a diagnosis of gestational related neoplasm: a population-based linkage study in Lombardy, 2010–2020

Background: A diagnosis of cancer during pregnancy or within one year after the end of pregnancy is a major clinical and public health issue. The current study aimed at estimating the incidence of pregnancy-associated cancer (PAC) and assessing whether the risk of abortion is increased in women diagnosed with cancer. Methods: This population-based cohort study used the regional healthcare utilization (HCU) databases of Lombardy, the largest region in Italy, to identify the women who delivered between 2010 and 2020. PAC were identified by oncological ICD-9-CM codes reported in the hospital discharge forms. We computed the ratio of PAC cases to the total number of pregnancies. Following a diagnosis of PAC, the prevalence ratio (PR) of abortion and the corresponding 95% confidence interval (CI), was estimated using a log-binomial model adjusted for maternal age. Results: During the study period, 926 women who gave birth (1.29 cases per 1000 births) and 341 women who had an abortion (1.52 cases per 1000 abortions) were diagnosed with PAC. Regardless of the outcome of pregnancy, the risk of PAC increased with increasing age. The rate of PAC was initially lower among births, but it came very close to the rate of PAC among abortions in the last two calendar years. The proportion of abortions among women with PAC gradually decreased from 27.7% in 2010–2012 to 18.5% in 2019–2020 (p-value < 0.001). Overall, a diagnosis of PAC was related to an approximately 10% increased risk of abortion (PR = 1.11, 95%CI:1.01–1.22). However, no association was observed in 2019–2020 (PR = 0.87, 95%CI:0.65–1.17). Considering only diagnoses made during the first trimester of pregnancy, the risk of abortion was about 2.5 times higher (PR = 2.53, 95%CI:2.05–3.11) and the risk of induced abortion was almost 4 times higher (PR = 3.71, 95%CI:2.82–4.90). Conclusion: In this population the risk of abortion was about 10% higher in women with PAC than in women without PAC. However, this association tended to decrease in more recent calendar periods. This trend seemed to be influenced more by spontaneous than by induced abortions.