A Retrospective Study of Mode of Delivery in Patients with Hypertrophic versus Other Forms of Cardiomyopathy.

BACKGROUND: A better understanding of optimal modes of birth is important to guide peripartum recommendations for patients with cardiomyopathy and may differ by cardiomyopathy type. OBJECTIVES: We sought to examine the association between mode of delivery and maternal morbidity events in patients with differing types of cardiomyopathy: hypertrophic, dilated, peripartum, and other/unspecified. STUDY DESIGN: This retrospective cohort study used the Premier Healthcare inpatient database, including patients aged 12 to 55 years who gave birth after 25 weeks' gestation with a diagnosis of cardiomyopathy between 2016 and 2020. Patients were categorized into hypertrophic, dilated, peripartum, or other/unspecified cardiomyopathy subtypes based on ICD-10 codes. Mode of delivery was classified as vaginal or cesarean. Cesarean was further classified as planned and intrapartum cesarean birth. The exposure was intended mode of delivery to simulate real life delivery planning decisions (vaginal delivery both completed and intrapartum cesarean birth versus planned cesarean birth). An analysis by actual mode of delivery was also performed (completed vaginal deliveries versus intrapartum cesarean delivery and planned cesarean delivery). Outcomes included severe maternal morbidity, blood transfusion, 90-day readmission, and inotrope use. Each outcome was analyzed by cardiomyopathy subtype. Statistical analyses included descriptive comparisons and multivariable logistic regression adjusting for age, insurance type, and comorbidities. RESULTS: There were 1872 births across cardiomyopathy subtypes. Amongst the subtypes, the peripartum cardiomyopathy group displayed the highest rates of intrapartum cesarean birth (34%) and severe maternal morbidity (32%), and hypertrophic cardiomyopathy the lowest rates (20% and 7%, respectively). There were no significant differences in severe maternal morbidity among patients with dilated (OR 1.50 [0.68-3.27]), peripartum (OR 1.32 [0.87-2.03]), or other (OR 0.80 [0.51-1.24]) cardiomyopathy when comparing intended cesarean vs intended vaginal birth. In contrast, in the hypertrophic cardiomyopathy group, the odds ratio was 3.73 [1.56-13.57] for severe maternal morbidity when comparing intended cesarean versus intended vaginal. In the analysis by actual mode of delivery, all cardiomyopathy subgroups had greater odds of severe maternal morbidity in cesarean versus vaginal birth: hypertrophic (OR 3.98 [1.06-14.91]), dilated (OR 4.05 [1.64-10.00]), peripartum (OR 2.47 [1.50-4.07]), and other (OR 2.18 [1.36-3.51]). Among patients who delivered via cesarean birth, odds of severe maternal morbidity were higher across all subgroups, and rates of severe maternal morbidity events among the group requiring intrapartum conversion to cesarean birth were high, suggesting this population to be at the highest risk CONCLUSIONS: : Among patients with hypertrophic cardiomyopathy, a trial of labor was associated with lower morbidity compared with a planned cesarean birth, implying either more morbid patients were selected for cesarean, or cesarean delivery was uniquely less optimal than vaginal delivery for hypertrophic cardiomyopathy patients in comparison to other cardiomyopathies in this cohort. While a trial of labor is the recommended mode of delivery for most patients with cardiomyopathy, the cardiomyopathy patients at greatest risk are those who require intrapartum conversion to cesarean. Prospective studies are needed to determine safe length of time in labor in these patients and factors leading to unplanned cesarean birth.