Abstract
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.
Keywords: cardiomyopathy, cardio-obstetrics, dilated cardiomyopathy, hypertrophic cardiomyopathy, inotrope, mode of delivery, peripartum cardiomyopathy
INTRODUCTION
The diagnosis of cardiomyopathy encompasses diverse etiologies with markedly different physiologic and hemodynamic profiles, each requiring tailored peripartum management and special considerations when determining mode of birth.1–4 For example, while preexisting cardiomyopathy in pregnancy is uncommon, affecting 76.1 (95% CI, 73.6–78.7) cases per 100,000 delivery hospitalizations, compared with peripartum cardiomyopathy, it is associated with a 2-fold increase in perinatal mortality.5
Further, in comparison to dilated cardiomyopathies, patients with hypertrophic cardiomyopathy generally tolerate the increased blood volume of pregnancy well, though they do remain at some risk for heart failure, arrhythmias, and syncope.6,7 Debate persists regarding the safest mode of birth in hypertrophic cardiomyopathy due to concerns about hemodynamic sensitivity with changes in preload and the hemodynamic effects of the Valsalva maneuver during vaginal birth. Compared with patients with hypertrophic cardiomyopathy, who may benefit from fluid resuscitation and typically do not require inotropic medications, those with heart failure with a reduced ejection fraction, including dilated or peripartum cardiomyopathy, frequently require fluid restriction, diuresis, or inotropic medications.3
A better understanding of optimal modes of birth (i.e., vaginal vs cesarean) is important to guide peripartum recommendations for patients with different etiologies of cardiomyopathy. Compared with vaginal births, cesarean births pose greater hemodynamic stress and increased risks of bleeding, thrombosis, embolism, and infection.1,2 However, patients with heart failure with reduced ejection fraction (HFrEF) may be unable to sufficiently augment cardiac output in response to the physiologic demands of pregnancy and labor, leading to increased risk of symptomatic heart failure and arrhythmias.3,8–10 Expert consensus suggests that a trial of labor is preferred for most patients with stable HFrEF (dilated and peripartum), reserving cesarean birth for those with hemodynamic instability, severe obstruction, or obstetric indications.2 In a recent retrospective cohort study of 2921 pregnant patients with cardiomyopathy, we found no increased maternal morbidity with vaginal birth compared with planned cesarean birth.11 However, further analysis by cardiomyopathy subtype is warranted due to differences in underlying pathophysiology.
The objective of this study was to examine the association of mode of delivery with maternal morbidity events, inotropic medication use, and hospital readmissions in patients with differing types of cardiomyopathy: hypertrophic, dilated, peripartum, and other/unspecified. We hypothesized that, across all subtypes of cardiomyopathy, a trial of labor would not confer higher risk of maternal morbidity when compared with planned cesarean birth. We also hypothesized that inotrope use would be higher in patients with dilated or peripartum cardiomyopathy and those requiring cesarean compared with vaginal birth. We aim to provide insights into the optimal management strategies specific to varying types of cardiomyopathies to inform future practice.
METHODS
After IRB review and exemption, a retrospective cohort study was conducted using the Premier Healthcare inpatient administrative database. The cardiomyopathy cohort consisted of patients 12 to 55 years from January 1, 2016, to September 30, 2020, who had International Classification of Diseases – Tenth Edition (ICD-10) diagnosis codes for both birth after 25 weeks’ gestation (Z3A.25-Z3A.42) and cardiomyopathy. Cardiomyopathy subtypes were hypertrophic (I42.1-I42.2), dilated (I42.0), peripartum (O90.3), and other/unspecified (I42.8-I42.9). Patients with both hypertrophic and other/unspecified cardiomyopathy were included in the hypertrophic subtype. Patients with both dilated and other/unspecified cardiomyopathy were included in the dilated subtype. Patients with both peripartum and other/unspecified cardiomyopathy were included in the peripartum subtype. Patients with any other combinations of cardiomyopathy diagnosis categories were excluded.
ICD-10 codes were also used to define vaginal birth and cesarean birth. Intrapartum cesarean births were defined by ICD-10 codes for cesarean birth plus fetal distress, failed operative birth, cord prolapse, fetal-maternal disproportion, obstructed labor, abnormal forces of labor, long labor, or failed induction (Supplemental Table 1).16 Cesarean births without evidence of labor were classified as ‘unlabored cesarean births’. We use the term 'unlabored' rather than 'planned' because clinical intent cannot be reliably determined from administrative data.
The exposure variable of interest was mode of delivery. Data were analyzed along an intention-to-treat basis compared presumed intended vaginal birth (vaginal birth and intrapartum cesarean birth) with intended cesarean birth (unlabored cesarean birth). The choice of this primary analysis was used to reflect clinical decision making when counseling pregnant patients on mode of delivery, as providers cannot know with certainty whether a trial of labor will result in a vaginal delivery or intrapartum cesarean. We also performed as-treated analyses, which compared completed vaginal birth with all cesarean births (intrapartum and unlabored cesarean birth). Outcomes were non-transfusion severe maternal morbidity (SMM) events (as defined by the Centers for Disease Control and Prevention) during birth hospitalization, blood transfusion (>4 units of packed red blood cells), readmission to birth hospital within 90 days, intensive care unit (ICU) stay, and inotropic medication use during birth hospitalization.23 These analyses were performed separately for all 4 cardiomyopathy subtypes.
Descriptive statistics were used to examine the study population. Patient characteristics were compared between groups using Wilcoxon rank sum tests and chi-squared or Fisher exact tests. Multivariable logistic regression models were used to compare outcomes by mode of delivery for both intention-to-treat and as-treated analyses. Covariates in the models were selected a priori and included age, payor category, and comorbidities (Supplemental Table 2).12 For the outcomes of SMM and readmission the non-transfusion weighted index was used and for the outcome of transfusion, the SMM weighted index was used.
RESULTS
Cohort
The cohort consisted of 1872 births: hypertrophic (n=233), dilated (n=203), peripartum (n=428), and other/unspecified (n=1008) cardiomyopathy (Figure 1). Baseline characteristics, including age, insurance status, hospital characteristics, and comorbidities, are shown in Table 1 and Supplemental Table 2. The rate of intrapartum cesarean birth (trial of labor resulting in cesarean birth) was highest for peripartum (34%) followed by other/unspecified (24%), dilated (24%), and hypertrophic (20%) cardiomyopathy. The rate of intrapartum cesarean birth was 15% for all deliveries in this Premier dataset. The rate of operative vaginal birth among completed vaginal birth was higher across the cardiomyopathy cohort, dilated (18%), peripartum (16%), hypertrophic (13%), and other/unspecified (8%), compared with the rate of 6% for all deliveries in Premier. The rates of preeclampsia with severe features or hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome among patients who delivered via cesarean birth were highest for peripartum (33%) followed by other/unspecified (11%), hypertrophic (11%), and dilated (10%) cardiomyopathy.
Figure 1.
Derivation of study cohort. ‘Intention-to-Treat’ analyses compared intended vaginal births (Vaginal + Intrapartum Cesarean) and intended cesarean births (Unlabored Cesarean). ‘As-Treated’ analyses compared actual vaginal births (Vaginal) and actual cesarean births (Intrapartum Cesarean + Unlabored Cesarean).
Table 1. Selected baseline characteristics for hypertrophic, dilated, peripartum, and other/unspecified cardiomyopathy subtypes.
Results reported as median [interquartile range] for age and number (percentage) for all other results.
| All completed VB | Intrapartum CB | Unlabored CB | Intention-to-treat: Intended Vaginal Birth (VB + Intrapartum CB) | As-treated: All Cesarean Births (Intrapartum + Unlabored CB) | P-value | ||||
|---|---|---|---|---|---|---|---|---|---|
| Intended | Actual | ||||||||
| Hypertrophic | n = 117 | n = 30 | n = 86 | n = 147 | n = 116 | ||||
| Age, years | 29 [25, 34] | 32 [25, 34] | 31 [27, 34] | 29 [25, 34] | 31 [27, 34] | 0.084 | 0.068 | ||
| Primary Payor | Managed Care | 44 (37.6%) | 10 (33.3%) | 28 (32.6%) | 54 (36.7%) | 38 (32.8%) | 0.165 | 0.514 | |
| Medicaid | 50 (42.7%) | 13 (43.3%) | 44 (51.2%) | 63 (42.9%) | 57 (49.1%) | ||||
| Medicare | 1 (0.9%) | 0 (0.0%) | 3 (3.5%) | 1 (0.7%) | 3 (2.6%) | ||||
| Other | 22 (18.8%) | 7 (23.3%) | 11 (12.8%) | 29 (19.7%) | 18 (15.5%) | ||||
| Prior Cesarean Birth | 6 (5.1%) | 3 (10.0%) | 40 (46.5%) | 9 (6.1%) | 43 (37.1%) | <0.001 | <0.001 | ||
| Multiple Gestation | 1 (0.9%) | 1 (3.3%) | 5 (5.8%) | 2 (1.4%) | 6 (5.2%) | 0.055 | 0.054 | ||
| Chronic Hypertension | 13 (11.1%) | 6 (20.0%) | 24 (27.9%) | 19 (12.9%) | 30 (25.9%) | 0.004 | 0.004 | ||
| PEC-SF / HELLP | 3 (2.6%) | 3 (10.0%) | 10 (11.6%) | 6 (4.1%) | 13 (11.2%) | 0.028 | 0.009 | ||
| Preterm Delivery | 17 (14.5%) | 9 (30.0%) | 33 (38.4%) | 26 (17.7%) | 42 (36.2%) | 0.001 | <0.001 | ||
| Dilated | n = 91 | n = 28 | n = 84 | n = 119 | n = 112 | ||||
| Age, years | 30 [25, 34] | 30 [25, 36] | 33 [29, 36] | 30 [25, 34] | 32 [28, 36] | 0.003 | 0.036 | ||
| Primary Payor | Managed Care | 27 (29.7%) | 12 (42.9%) | 21 (25.0%) | 39 (32.8%) | 33 (29.5%) | 0.043 | 0.171 | |
| Medicaid | 49 (53.8%) | 10 (35.7%) | 43 (51.2%) | 59 (49.6%) | 53 (47.3%) | ||||
| Medicare | 2 (2.2%) | 1 (3.6%) | 10 (11.9%) | 3 (2.5%) | 11 (9.8%) | ||||
| Other | 13 (14.3%) | 5 (17.9%) | 10 (11.9%) | 18 (15.1%) | 15 (13.4%) | ||||
| Prior Cesarean Birth | 3 (3.3%) | 10 (35.7%) | 42 (50.0%) | 13 (10.9%) | 52 (46.4%) | <0.001 | <0.001 | ||
| Multiple Gestation | 2 (2.2%) | 0 (0.0%) | 7 (8.3%) | 2 (1.7%) | 7 (6.3%) | 0.023 | 0.163 | ||
| Chronic Hypertension | 26 (28.6%) | 9 (32.1%) | 29 (34.5%) | 35 (29.4%) | 38 (33.9%) | 0.440 | 0.414 | ||
| PEC-SF / HELLP | 4 (4.4%) | 5 (17.9%) | 6 (7.1%) | 9 (7.6%) | 11 (9.8%) | 0.910 | 0.142 | ||
| Preterm Delivery | 24 (26.4%) | 15 (53.6%) | 52 (61.9%) | 39 (32.8%) | 67 (59.8%) | <0.001 | <0.001 | ||
| Peripartum | n = 147 | n = 74 | n = 207 | n = 221 | n = 281 | ||||
| Age, years | 29 [25, 34] | 31 [25, 36] | 30 [26, 35] | 30 [25, 35] | 30 [26, 35] | 0.700 | 0.236 | ||
| Primary Payor | Managed Care | 33 (22.4%) | 25 (33.8%) | 52 (25.1%) | 58 (26.2%) | 77 (27.4%) | 0.613 | 0.164 | |
| Medicaid | 96 (65.3%) | 37 (50.0%) | 118 (57.0%) | 133 (60.2%) | 155 (55.2%) | ||||
| Medicare | 7 (4.8%) | 3 (4.1%) | 10 (4.8%) | 10 (4.5%) | 13 (4.6%) | ||||
| Other | 11 (7.5%) | 9 (12.2%) | 27 (13.0%) | 20 (9.0%) | 36 (12.8%) | ||||
| Prior Cesarean Birth | 4 (2.7%) | 20 (27.0%) | 92 (44.4%) | 24 (10.9%) | 112 (39.9%) | <0.001 | <0.001 | ||
| Multiple Gestation | 2 (1.4%) | 3 (4.1%) | 20 (9.7%) | 5 (2.3%) | 23 (8.2%) | 0.001 | 0.004 | ||
| Chronic Hypertension | 25 (17.0%) | 19 (25.7%) | 53 (25.6%) | 44 (19.9%) | 72 (25.6%) | 0.160 | 0.043 | ||
| PEC-SF / HELLP | 21 (14.3%) | 25 (33.8%) | 68 (32.9%) | 46 (20.8%) | 93 (33.1%) | 0.005 | <0.001 | ||
| Preterm Delivery | 57 (38.8%) | 48 (64.9%) | 125 (60.4%) | 105 (47.5%) | 173 (61.6%) | 0.008 | <0.001 | ||
| Other/Unspecified | n = 477 | n = 153 | n = 378 | n = 630 | n = 531 | ||||
| Age, years | 31 [26, 36] | 32 [26, 36] | 32 [28, 36] | 31 [26, 36] | 32 [28, 36] | 0.010 | 0.033 | ||
| Primary Payor | Managed Care | 144 (30.2%) | 52 (34.0%) | 109 (28.8%) | 196 (31.1%) | 161 (30.3%) | 0.249 | 0.047 | |
| Medicaid | 250 (52.4%) | 74 (48.4%) | 192 (50.8%) | 324 (51.4%) | 266 (50.1%) | ||||
| Medicare | 13 (2.7%) | 10 (6.5%) | 24 (6.3%) | 23 (3.7%) | 34 (6.4%) | ||||
| Other | 70 (14.7%) | 17 (11.1%) | 53 (14.0%) | 87 (13.8%) | 70 (13.2%) | ||||
| Prior Cesarean Birth | 30 (6.3%) | 36 (23.5%) | 233 (61.6%) | 66 (10.5%) | 269 (50.7%) | <0.001 | <0.001 | ||
| Multiple Gestation | 9 (1.9%) | 3 (2.0%) | 22 (5.8%) | 12 (1.9%) | 25 (4.7%) | 0.001 | 0.013 | ||
| Chronic Hypertension | 110 (23.1%) | 58 (37.9%) | 123 (32.5%) | 168 (26.7%) | 181 (34.1%) | 0.046 | <0.001 | ||
| PEC-SF / HELLP | 17 (3.6%) | 26 (17.0%) | 34 (9.0%) | 43 (6.8%) | 60 (11.3%) | 0.209 | <0.001 | ||
| Preterm Delivery | 92 (19.3%) | 91 (59.5%) | 156 (41.3%) | 183 (29.0%) | 247 (46.5%) | <0.001 | <0.001 | ||
Abbreviations: VB = Vaginal Birth; CB = Cesarean Birth; Intended VB = VB + Intrapartum CB; All CB = Intrapartum CB + Unlabored CB; PEC-SF = Preeclampsia with Severe Features; HELLP = Hemolysis, Elevated Liver enzymes, and Low Platelets.
Severe Maternal Morbidity
Crude incidence of SMM events was highest for peripartum (32%) followed by dilated (18%), other/unspecified (11%), and hypertrophic (7%) cardiomyopathy (Table 2). Across all cardiomyopathy groups, SMM events occurred more frequently during cesarean birth compared with vaginal birth. For all cardiomyopathy groups except hypertrophic, SMM events were more frequent during intrapartum cesarean birth compared with unlabored cesarean birth. In the hypertrophic cohort, intended vaginal birth (including intrapartum cesarean birth) had lower rates of SMM than planned cesarean birth (3.4% vs 14%, P = .003). The most common SMM in the hypertrophic cardiomyopathy group were acute respiratory distress syndrome (5.8%), acute heart failure (3.5%), acute renal failure (3.5%), and disseminated intravascular coagulation (3.5%) (Supplemental Table 3). Among the 15 patients with hypertrophic cardiomyopathy who required operative vaginal birth, there was only one episode of SMM (conversion of cardiac rhythm). In the dilated cardiomyopathy group, the most common SMM events were acute respiratory distress syndrome (8.2%), acute renal failure (7.8%), ventilation (7.4%), shock (7.3%), and acute heart failure (6.9%). In the peripartum cardiomyopathy group, the most common SMM events were ventilation (15.8%), acute respiratory distress syndrome (12.3%), acute heart failure (9.1%), shock (6.5%), and acute renal failure (6.5%) (Supplemental Table 3).
Table 2. Selected outcomes for hypertrophic, dilated, peripartum, and other/unspecified cardiomyopathy subtypes.
Results reported as median [interquartile range] for length of stay after delivery and number (percentage) for all other results.
| All Completed VB | Intrapartum CB | Unlabored CB | Intention-to-treat: Intended Vaginal Birth (VB + Intrapartum CB) | As-treated: All Cesarean Births (Intrapartum + Unlabored CB) | P-value | |||
|---|---|---|---|---|---|---|---|---|
| Intended | Actual | |||||||
| Hypertrophic | SMM Event (Composite) | 3 (2.6%) | 2 (6.7%) | 12 (14.0%) | 5 (3.4%) | 14 (12.1%) | 0.003 | 0.005 |
| Intensive Care Stay | 6 (5.1%) | 9 (30.0%) | 20 (23.3%) | 15 (10.2%) | 29 (25.0%) | 0.007 | <0.001 | |
| Length of Stay after Delivery | 1 [1, 1] | 2 [2, 3] | 2 [1, 3] | 1 [1, 2] | 2 [2, 3] | <0.001 | <0.001 | |
| 42-Day Hospital Readmission | 1 (0.9%) | 4 (13.3%) | 8 (9.3%) | 5 (3.4%) | 12 (10.3%) | 0.058 | 0.002 | |
| 90-Day Hospital Readmission | 2 (1.7%) | 4 (13.3%) | 8 (9.3%) | 6 (4.1%) | 12 (10.3%) | 0.106 | 0.006 | |
| Any Inotrope Use | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | N/A | N/A | |
| <4 Units pRBC Blood Transfusion | 1 (0.9%) | 2 (6.7%) | 14 (16.3%) | 3 (2.0%) | 16 (13.8%) | <0.001 | <0.001 | |
| ≥4 Units pRBC Blood Transfusion | 1 (0.9%) | 1 (3.3%) | 2 (2.3%) | 2 (1.4%) | 3 (2.6%) | 0.627 | 0.370 | |
| Dilated | SMM Event (Composite) | 7 (7.7%) | 10 (35.7%) | 19 (22.6%) | 17 (14.3%) | 29 (25.9%) | 0.126 | 0.001 |
| Intensive Care Stay | 21 (23.1%) | 13 (46.4%) | 38 (45.2%) | 34 (28.6%) | 51 (45.5%) | 0.015 | 0.001 | |
| Length of Stay after Delivery | 1 [1, 2] | 2 [2, 5] | 3 [2, 4] | 1 [1, 2] | 3 [2, 4] | <0.001 | <0.001 | |
| 42-Day Hospital Readmission | 3 (3.3%) | 4 (14.3%) | 7 (8.3%) | 7 (5.9%) | 11 (9.8%) | 0.497 | 0.068 | |
| 90-Day Hospital Readmission | 3 (3.3%) | 4 (14.3%) | 7 (8.3%) | 7 (5.9%) | 11 (9.8%) | 0.497 | 0.068 | |
| Any Inotrope Use | 7 (7.7%) | 5 (17.9%) | 8 (9.5%) | 12 (10.1%) | 13 (11.6%) | 0.895 | 0.352 | |
| <4 Units pRBC Blood Transfusion | 9 (9.9%) | 3 (10.7%) | 8 (9.5%) | 12 (10.1%) | 11 (9.8%) | >0.999 | >0.999 | |
| ≥4 Units pRBC Blood Transfusion | 2 (2.2%) | 2 (7.1%) | 7 (8.3%) | 4 (3.4%) | 9 (8.0%) | 0.206 | 0.116 | |
| Peripartum | SMM Event (Composite) | 27 (18.4%) | 36 (48.6%) | 73 (35.3%) | 63 (28.5%) | 109 (38.8%) | 0.133 | <0.001 |
| Intensive Care Stay | 43 (29.3%) | 41 (55.4%) | 105 (50.7%) | 84 (38.0%) | 146 (52.0%) | 0.008 | <0.001 | |
| Length of Stay after Delivery | 1 [1, 3] | 4 [2, 5] | 3 [2, 5] | 2 [1, 4] | 3 [2, 5] | 0.008 | <0.001 | |
| 42-Day Hospital Readmission | 11 (7.5%) | 6 (8.1%) | 17 (8.2%) | 17 (7.7%) | 23 (8.2%) | 0.842 | 0.799 | |
| 90-Day Hospital Readmission | 11 (7.5%) | 6 (8.1%) | 17 (8.2%) | 17 (7.7%) | 23 (8.2%) | 0.842 | 0.799 | |
| Any Inotrope Use | 13 (8.8%) | 8 (10.8%) | 18 (8.7%) | 21 (9.5%) | 26 (9.3%) | 0.772 | 0.889 | |
| <4 Units pRBC Blood Transfusion | 18 (12.2%) | 15 (20.3%) | 32 (15.5%) | 33 (14.9%) | 47 (16.7%) | 0.894 | 0.257 | |
| ≥4 Units pRBC Blood Transfusion | 3 (2.0%) | 9 (12.2%) | 7 (3.4%) | 12 (5.4%) | 16 (5.7%) | 0.353 | 0.089 | |
| Other/Unspecified | SMM Event (Composite) | 28 (5.9%) | 40 (26.1%) | 41 (10.8%) | 68 (10.8%) | 81 (15.3%) | 0.979 | <0.001 |
| Intensive Care Stay | 50 (10.5%) | 53 (34.6%) | 80 (21.2%) | 103 (16.3%) | 133 (25.0%) | 0.055 | <0.001 | |
| Length of Stay after Delivery | 1 [1, 1] | 3 [2, 4] | 2 [2, 3] | 1 [1, 2] | 2 [2, 3] | <0.001 | <0.001 | |
| 42-Day Hospital Readmission | 26 (5.5%) | 13 (8.5%) | 14 (3.7%) | 39 (6.2%) | 27 (5.1%) | 0.087 | 0.795 | |
| 90-Day Hospital Readmission | 26 (5.5%) | 13 (8.5%) | 14 (3.7%) | 39 (6.2%) | 27 (5.1%) | 0.087 | 0.795 | |
| Any Inotrope Use | 30 (6.3%) | 15 (9.8%) | 21 (5.6%) | 45 (7.1%) | 36 (6.8%) | 0.324 | 0.753 | |
| <4 Units pRBC Blood Transfusion | 17 (3.6%) | 22 (14.4%) | 31 (8.2%) | 39 (6.2%) | 53 (10.0%) | 0.250 | <0.001 | |
| ≥4 Units pRBC Blood Transfusion | 3 (0.6%) | 7 (4.6%) | 13 (3.4%) | 10 (1.6%) | 20 (3.8%) | 0.079 | 0.001 | |
Abbreviations: VB = Vaginal Birth; CB = Cesarean Birth; Intended VB = VB + Intrapartum CB; All CB = Intrapartum CB + Unlabored CB; SMM = Severe Maternal Morbidity; pRBC = Packed Red Blood Cells.
Patients with peripartum cardiomyopathy had a higher rate of SMM when compared with the previously published full cohort comprising all types of cardiomyopathies (31.7% vs 14.8%, respectively).11 This increased rate of SMM in patients with peripartum cardiomyopathy was observed across all three modes of delivery when compared with the overall cohort of cardiomyopathy patients (Supplemental Table 3).
In the primary analysis comparing intended vaginal birth compared with intended cesarean birth, there were differences noted across cardiomyopathy type (Figure 2, Table 2, Supplemental Tables 3–4). Comparing intended cesarean birth with intended vaginal birth, there were higher odds of SMM with intended cesarean birth among patients with hypertrophic cardiomyopathy (OR 3.73 [1.18–11.82]). There were no significant differences in odds of SMM 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 for intended cesarean vs intended vaginal birth.
Figure 2.
Unadjusted odds ratios for outcomes. Intended (blue) and actual (orange) modes of delivery (cesarean vs vaginal) for (a) severe maternal morbidity, (b) >4 units packed red blood cell transfusion, (c) 90-day hospital readmission, and (d) inotrope use by cardiomyopathy subtype.
In the secondary analysis reclassifying patients based on their actual delivery route (regardless of whether a trial of labor was attempted), among patients who actually underwent cesarean birth versus vaginal birth, there were increased odds of severe morbidity among all cardiomyopathy subgroups: 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]) (Table 3).
Table 3.
Odds of severe maternal morbidity by cardiomyopathy subtype.
| Mode of Delivery | Odds Ratio | 95% CI | Interpretation | |
|---|---|---|---|---|
| Hypertrophic | Intended | 3.73 | 1.18–11.82 | Higher Morbidity with intended cesarean |
| Actual | 3.98 | 1.06–14.91 | Higher morbidity with actual cesarean | |
| Dilated | Intended | 1.50 | 0.68–3.27 | No increased risk with trial of labor |
| Actual | 4.05 | 1.64–10.00 | Higher morbidity with actual cesarean | |
| Peripartum | Intended | 1.32 | 0.87–2.03 | No increased risk with trial of labor |
| Actual | 2.47 | 1.50–4.07 | Higher morbidity with actual cesarean | |
| Other/Unspecified | Intended | 0.80 | 0.51–1.24 | No increased risk with trial of labor |
| Actual | 2.18 | 1.24–14.95 | Higher morbidity with actual cesarean |
Blood Transfusion
Rates of blood transfusion (>4 units) varied by cardiomyopathy subtype, with the lowest rates of transfusion among patients with hypertrophic cardiomyopathy (0.9% for vaginal birth, 3.3% for intrapartum cesarean, and 2.3% for planned cesarean), followed by other cardiomyopathy (0.6% vaginal birth, 4.6% intrapartum cesarean, 3.4% planned cesarean). Patients with dilated cardiomyopathy received transfusion with >4 units pRBC for 2.2% of vaginal birth, 7.1% of intrapartum cesarean, and 8.3% of planned cesarean births, while patients with peripartum cardiomyopathy received transfusion for 2.0% of vaginal birth, 12.2% of intrapartum cesarean, and 3.4% of planned cesarean birth (Table 2).
For the intention-to-treat analysis, there was no statistically significant difference in risk of transfusion among any subgroup for intended cesarean vs intended vaginal delivery. For the as-treated analysis, the other cardiomyopathy subgroup had a higher odds of transfusion (OR 4.30 [1.24–14.95]) with cesarean delivery.
ICU Care and Hospital Readmission
For the hypertrophic cardiomyopathy group, intensive care unit (ICU) care was required significantly more frequently for cesarean birth compared with vaginal birth in both intention-to-treat (23.3% vs 10.2%, P = .007) and as-treated (25.0% vs 5.1%, P < .001) analyses, although this group had lower rates of ICU care compared with other subtypes (Table 2). For peripartum cardiomyopathy, ICU care was more frequently required for cesarean birth compared with vaginal birth in both the intention-to-treat (57.8% vs 38.3%, P = .008) and as-treated (52.0% vs 29.3%, P<.001) analysis. Similarly, for dilated cardiomyopathy, ICU care was more frequently required for cesarean compared with vaginal birth for both intention-to-treat and as treated analyses.
Patients with peripartum cardiomyopathy had a higher rate of ICU stay among all modes of deliveries when compared with the full cohort of cardiomyopathies (all cardiomyopathies: vaginal birth 13.4%, intrapartum cesarean birth 29.6%, and cesarean birth 29.4%; peripartum cardiomyopathy: vaginal birth 29.3%, intrapartum cesarean birth 55.4%, and cesarean birth 50.7%).11 Among patients with peripartum cardiomyopathy, there was a significantly higher prevalence of ICU stay with cesarean birth in both primary (vaginal birth 38% vs unlabored cesarean 50.7%, P = .008) and secondary (as-treated vaginal birth 29.3% vs as-treated cesarean birth 52%, P < .001) analysis. Among the intention-to-treat analysis, there was no significant difference between 90-day readmission intended cesarean and intended vaginal delivery for any subgroup. For the as-treated analysis, cesarean delivery was associated with higher odds of readmission (OR 5.36 [1.14–25.21]) compared with vaginal delivery.
Inotrope Use
For patients with dilated cardiomyopathy, inotrope use was higher in cesarean birth compared with vaginal birth in both intention-to-treat (OR 4.62 [1.38–15.47]) and as-treated (OR 13.64 [1.75–106.62]) analyses (Supplemental Table 4). Inotropes were used between 3 days before and 7 days after birth. The percentage of patients receiving any inotrope during this period varied between 2% to 6% and was highest on the day of birth. The day of highest use was 2 days prior to birth for dopamine, on the day of birth for epinephrine and dobutamine, and 7 days after birth for milrinone.
For patients with peripartum cardiomyopathy, there were no significant differences between cesarean birth and vaginal birth for inotrope use in intention-to-treat analyses. In as-treated analyses, patients who had a cesarean birth were significantly more likely to use inotropes (17.4% vs 5.4%, P = .001) compared with vaginal birth. Patients who had a cesarean birth had a significantly increased odds of inotrope use compared with vaginal birth (OR 3.37 [1.52–7.47]). For patients with other cardiomyopathy, there was no significant difference in inotrope use in the intention-to-treat analysis. For the as-treated analysis, patients who underwent cesarean birth had a significantly higher odds of inotrope use (OR 9.70 [2.26–41.59]). No inotropes were used for any patients with hypertrophic cardiomyopathy.
Mortality
Across the entire cohort, there were 10 in-hospital mortality events: 7 in the other/unspecified cardiomyopathy group (3 vaginal birth, 3 intrapartum cesarean birth, 1 unlabored cesarean birth) and 3 in the peripartum cardiomyopathy group (1 vaginal birth, 2 unlabored cesarean birth) (Supplemental Table 3). There were no mortality events in either the hypertrophic or dilated cardiomyopathy groups.
COMMENT
Principal Findings
In this cohort, across all subtypes of cardiomyopathy, a trial of labor was not associated with greater SMM when compared with unlabored cesarean birth. In patients with hypertrophic cardiomyopathy, a trial of labor was associated with lower odds of SMM when compared with unlabored cesarean birth. However, among patients who delivered via cesarean birth, odds of SMM were higher across all subgroups, and rates of SMM events among the group requiring intrapartum conversion to cesarean birth were high, suggesting this population to be at the highest risk. Notably, rates of intrapartum conversion to cesarean birth and rates of SMM events varied across subtypes of cardiomyopathy.
Clinical Implications
These findings highlight important differences in the risks associated with mode of delivery across clinical populations. Risks can be related to the procedure itself or differences in patient disease and its severity. In individuals with dilated, peripartum, or other cardiomyopathy, the primary analysis did not show a statistically significant difference in morbidity by intended delivery mode, suggesting that trial of labor may be a reasonable and safe option in well-selected patients. However, the secondary analysis demonstrated a marked increase in morbidity among those who underwent cesarean birth, particularly intrapartum cesarean, reinforcing the importance of careful labor planning, real-time cardiac monitoring, and vigilance about mitigating increased risks when trial of labor is unsuccessful in these patients. Although obstetric indications for cesarean may arise in any patient, patients with cardiomyopathy who are selected to undergo a trial of labor should have a favorable a priori chance of successful vaginal birth such as younger maternal age, lower body mass index and gestational weight gain, and a favorable cervical exam.13,14 The elevated operative vaginal birth rates in the cardiomyopathy cohort (8% – 18%) versus the general Premier population (6%) likely reflect deliberate shortening of the second stage. The risks and benefits of operative vaginal delivery are an important consideration when selecting mode of delivery. The choice to perform a planned cesarean delivery to avoid possible maternal and neonatal morbidity from operative delivery when prolonged Valsalva is contraindicated is reasonable and may be desired by some patients.
In contrast to other cardiomyopathy subtypes, in the hypertrophic cardiomyopathy group, both analyses favored vaginal birth over cesarean, even among the patients who underwent a trial of labor but ultimately required cesarean birth. These findings suggest that a trial of vaginal birth is preferred in this population, and underscores the knowledge that, compared with other types of cardiomyopathy, the hemodynamic changes of pregnancy and labor are generally well-tolerated in hypertrophic cardiomyopathy.15,16
Research Implications
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 multicenter cardio-obstetric registries with detailed cardiovascular phenotyping, clinician-adjudicated diagnoses, and standardized collection of maternal, obstetric, and institutional factors will be essential to identify patients at highest risk for intrapartum cesarean delivery, optimize delivery planning, and refine individualized recommendations regarding mode of delivery.
Strengths and Limitations
Limitations of this study relate primarily to the nature of the dataset. As an administrative dataset relying on billing and diagnosis codes, the Premier Inpatient Dataset lacks granular clinical detail: over half the population has an unspecified cardiomyopathy type, New York Heart Association functional class is unavailable,6 and echocardiographic parameters were not captured. Access to left ventricular ejection fraction would likely have been both prognostic for severity of illness and lower LVEF would likely be associated with planned cesarean birth.
Since diagnosis codes are assigned primarily for billing rather than research purposes, administrative datasets are susceptible to diagnostic misclassification. We could not perform validation of accuracy of ICD-10 coding for cardiomyopathy subtype within the Premier Healthcare Database. Consequently, diagnostic misclassification is possible, particularly for specific cardiomyopathy subtypes. Such misclassification could have attenuated observed differences between groups and may partially explain the large proportion of patients classified as having unspecified or other cardiomyopathy. The large proportion of patients classified as having other or unspecified cardiomyopathy likely reflects, at least in part, limitations of administrative coding and the absence of detailed clinical phenotyping. This limitation is particularly important because this heterogeneous subgroup demonstrated the highest observed rates of adverse maternal outcomes. Future studies using prospective registries or clinician-adjudicated diagnoses are needed to confirm these findings. While large administrative datasets provide sufficient sample sizes to study rare conditions such as cardiomyopathy in pregnancy, they lack the detailed cardiovascular phenotyping necessary for individualized risk assessment. Future prospective multicenter registries incorporating NYHA functional class, mWHO classification, echocardiographic parameters, and other measures of disease severity will be essential to refine delivery recommendations and improve patient counseling.
For the hypertrophic cardiomyopathy cohort specifically, the absence of LVOT gradient and Valsalva symptom data is notable, as patients with severe left ventricular outflow tract obstruction or Valsalva-provoked symptoms are often recommended for planned cesarean birth. Similarly, we were unable to distinguish obstructive from non-obstructive hypertrophic cardiomyopathy, despite important differences in pathophysiology, management, and pregnancy risk between these phenotypes. Because of this limitation of the dataset, we were unable to evaluate whether delivery outcomes vary between these important clinical subgroups.
The dataset also does not capture acuity of diagnosis, which would likely influence both mode of delivery decisions and maternal morbidity outcomes. A patient presenting with acute decompensated heart failure and a new cardiomyopathy diagnosis is likely more acutely ill than one with a known, monitored cardiomyopathy or a prior peripartum cardiomyopathy diagnosis with recovered LVEF. Likewise, the database does not distinguish spontaneous preterm birth from medically indicated preterm delivery. Because medically indicated preterm birth may reflect worsening maternal cardiovascular status or obstetric complications, we were unable to determine the extent to which preterm delivery influenced decisions regarding induction of labor or planned cesarean birth.
Coding used to identify indications for cesarean delivery are likely applied imprecisely, and misclassification bias between patients with unlabored and intrapartum cesarean delivery is possible. Institutional characteristics that likely influence maternal outcomes including maternal level of care designation, availability of dedicated cardio-obstetrics programs, multidisciplinary expertise, and access to specialized cardiovascular, obstetric, anesthesiology, and neonatal services were not available in this administrative dataset. Future registries should incorporate these healthcare system variables to better evaluate the influence of care delivery models on maternal and neonatal outcomes.
The inclusion of the COVID-19 pandemic in the final year of the dataset may have altered delivery practice patterns. Several analyses yielded wide confidence intervals, reflecting the low frequency of cardiomyopathy in pregnancy and the small number of events within specific cardiomyopathy subtypes and delivery mode strata. Accordingly, some effect estimates should be interpreted cautiously and considered hypothesis-generating. Larger prospective multicenter registries will be important to provide more precise estimates of risk. Our analysis did not include adjustment for race. In peripartum cardiomyopathy, race is associated with worse outcome, including presentation with lower LVEF and higher mortality rates.24–25 The reasons for this within the United States are likely to be multifactorial but may include social determinants of health, racism, and access to care. In our previous analysis of the Premier dataset, we found that payor status statistically captured much of the variation associated with race and ethnicity, and thus this was used in our analysis.17 However, it is likely that there are other factors related to race and outcome not captured by this variable.
Despite these limitations, large administrative datasets remain uniquely valuable for studying rare conditions such as cardiomyopathy in pregnancy because they provide sample sizes that are otherwise difficult to achieve. Future prospective multicenter cardio-obstetric registries incorporating clinician-adjudicated diagnoses, detailed cardiovascular phenotyping, echocardiographic parameters, delivery indications, institutional characteristics, and longitudinal maternal outcomes will be essential to validate these findings and refine individualized delivery recommendations for patients with cardiomyopathy
Conclusions
Overall, this analysis underscores the value of individualized, condition-specific delivery planning. Our data suggests that in patients with cardiomyopathies diagnosed or known antepartum, in appropriately selected patients, a trial of labor does not significantly increase maternal morbidity, blood transfusion risk, or readmission rates compared with cesarean birth.
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 a 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.
Supplementary Material
CONDENSATION PAGE.
Short title:
Type of cardiomyopathy and mode of delivery
AJOG at a glance:
A. Why was this study conducted?
To examine how cardiomyopathy types with distinct hemodynamic challenges affect maternal outcomes based on mode of delivery.
B. What are the key findings?
Among patients with hypertrophic cardiomyopathy, a trial of labor was associated with lower morbidity compared with a planned cesarean birth.
Among patients with dilated, peripartum or other cardiomyopathy, cesarean birth was associated with higher odds of inotrope use.
C. What does this study add to what is already known?
Among pregnant patients with hypertrophic, dilated, and peripartum cardiomyopathy, a trial of labor does not significantly increase the risk of maternal morbidity, blood transfusion, or hospital readmission compared with cesarean birth.
However, patients who delivered by unscheduled cesarean birth had higher odds of morbidity compared with vaginal delivery or planned cesarean.
Funding:
This work was supported in part by a grant to Dr. Federspiel from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (K12HD103083). The content in this manuscript is solely the responsibility of the authors and does not in any way represent the official views of the funders.
Footnotes
Disclosures: Dr. Federspiel discloses consulting for Noma AI, Grifols, UCB, and Sanofi, and receiving research funding from Koko Medical. The other authors report no disclosures.
Prior presentation:
Portions of this work were presented at the Cardiac Problems in Pregnancy Conference in Vienna Austria, April 2025.
Declaration of generative AI and AI-assisted technologies in the manuscript preparation process: During the preparation of this work the author(s) used Copilot and ChatGPT in order to shorten text written by authors. After using this tool/service, the author(s) reviewed and edited the content as needed and take(s) full responsibility for the content of the published article.
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