(1190) Risk of severe maternal morbidity among pregnant people with breast cancer using a population database

Objective:
A new breast cancer diagnosis is more common than all other cancer types in females 15-39 years in the United States and is the second leading cause of female cancer deaths. Our objective was to determine the odds of severe maternal morbidity (SMM) in breast cancer in pregnancy using TriNetX, a research network containing real-world data from 93 health care organizations and > 131 million patients.


Study Design: This retrospective cohort study queried TriNetX from inception to 8/2024 for subjects 12-55 years with a pregnancy diagnosis. Two cohorts were derived: (1) individuals with an active diagnosis of breast cancer 1 year prior to, or up to 1 month after, first instance of pregnancy and (2) those without a history of any cancer type in pregnancy. Cohorts were propensity score matched 1:1 by demographics and comorbidities by TriNetX built-in analysis tools. SMM was defined as CDC’s 21 indicators and corresponding ICD-10 codes. The primary outcome was odds ratio (OR) between cohorts of composite SMM occurring up to 1 year after first instance of pregnancy. Secondary outcomes were odds of individual indicators of SMM. All statistical analyses were conducted in the TriNetX platform.

Results:
Propensity score matching yielded 9937 cases of breast cancer in pregnancy and 9937 cases of pregnancy without cancer history (Table). Subjects with breast cancer in pregnancy had significantly higher odds of composite SMM (OR 3.61 (95% confidence interval (CI) 3.17-4.12), p< 0.001) compared to those without malignancy in pregnancy. The odds of acute respiratory distress syndrome (ARDS) were highest (OR 3.89 (95% CI 3.31-4.56), p< 0.001), followed by cerebrovascular disorders (OR 3.30 (95% CI 2.73-3.98), p< 0.001) and disseminated intravascular coagulation (DIC) (OR 3.01 (95% CI 2.47-3.67), p< 0.001).


Conclusion: Individuals with breast cancer in pregnancy have more than three-fold increased odds of composite SMM compared to those without cancer history, with considerably higher risk of ARDS, cerebrovascular disorders, and DIC.