Association of Pre-pregnancy Body Mass Index with Peripartum Cardiomyopathy
Keywords:  Department Medicine
obesity
comorbidity
heart failure
pregnancy
hypertensive disorder
cardiovascular disease
maternal health
population health
pregnancy complication
Community Health and Prevention Research
Stanford Prevention Research Center
Stanford Medicine
Stanford University School of Medicine
Obstetrics and Gynecology
Maternal Fetal Medicine
Thesis

Objective: To determine the association of pre-pregnancy body mass index (BMI) with peripartum cardiomyopathy, and whether the association varies among women with and without pregnancy-related hypertensive disorders
Background: In recent decades, the prevalence of peripartum cardiomyopathy has increased in the US. Cardiomyopathy is one of the common causes of maternal morbidity, and is the leading cause of death in the late postpartum period. One suggested explanation is the increasing prevalence of obesity. However, evidence for an association and contribution of maternal obesity to the development of cardiomyopathy is limited.
Methods: This population-based study used linked birth record and patient discharge data from live births in California during 2007-2012 (n=2,548,380). The peripartum cardiomyopathy case group included all patients with peripartum cardiomyopathy diagnosis at birth hospitalization or readmission within five months of birth. BMI was categorized into 5 groups: normal weight (18.5-24.9), overweight (25.0-29.9), obesity class 1 (30.0-34.9), obesity class 2 (35.0-39.9), and obesity class 3 (>40). We excluded women with underweight BMI given its infrequent co-occurrence with cardiomyopathy. Obesity classes were combined into one group (> 30) to ensure sufficient power for some analyses. Multivariable logistic regression was used to estimate the association of pre-pregnancy BMI with peripartum cardiomyopathy through odds ratios (ORs) with 95% confidence intervals, adjusted for maternal age, race/ethnicity, education, healthcare coverage, parity, plurality, and comorbidities. To consider interaction between pre-pregnancy BMI and pregnancy-related hypertensive disorders, separate regression models were conducted for women with and without pregnancy-related hypertensive disorders.
Results: The prevalence of peripartum cardiomyopathy was 13 per 100,000 live births (n=320). Unadjusted ORs were 1.32 (95% CI, 1.01-1.74) for overweight women; 1.59 (95% CI, 1.15-2.20) for women with class 1 obesity; 2.22 (95% CI, 1.48-3.32) for women with class 2 obesity; and 3.55 (95% CI, 2.34-5.37) for women with class 3 obesity, compared with women with normal pre-pregnancy BMI. Adjusted ORs were 1.26 (95% CI, 0.95-1.66) for overweight women; 1.30 (95% CI, 0.93-1.82) for women with class 1 obesity; 1.42 (95% CI, 0.93-2.18) for women with class 2 obesity; and 1.57 (95% CI, 1.00-2.47) for women with class 3 obesity, compared with women with normal pre-pregnancy BMI. When further adjusted for pregnancy-related hypertensive disorders, adjusted ORs were 1.16 (95% CI, 0.88-1.54); 1.15 (95% CI, 0.82-1.61); 1.24 (95% CI, 0.81-1.89); and 1.36 (95% CI, 0.87-2.12), respectively. Stratified analysis suggested that the increased risk of peripartum cardiomyopathy among women with overweight and obese BMI was only present among women who did not have pregnancy-related hypertensive disorders (P for interaction < 0.001).
Conclusion: Among women in California, increasing pre-pregnancy BMI was associated with increasing risk of peripartum cardiomyopathy, but only among women who did not have pregnancy-related hypertensive disorders.