Mode of delivery and perinatal outcomes by modified World Health Organization classification of maternal cardiovascular risk in pregnancy

Abstract

BACKGROUND:

Cardiac disease is a leading cause of maternal morbidity and mortality in the United States, and an increasing number of patients with known cardiac disease are reaching childbearing age. Although guidelines indicate that cesarean deliveries should be reserved for obstetrical indications, rates of cesarean delivery among obstetrical patients with cardiovascular disease are higher than those of the general population.

OBJECTIVE:

This study aimed to evaluate mode of delivery and perinatal outcomes among patients with low-risk and moderate to high–risk cardiac disease as defined by the modified World Health Organization classification of maternal cardiovascular risk.

STUDY DESIGN:

We performed a retrospective cohort study of obstetrical patients with known cardiac disease, as defined by the modified World Health Organization cardiovascular classification categories in pregnancy, who underwent a perinatal transthoracic echocardiogram at a single academic medical center between October 1, 2017 and May 1, 2022. Demographics, clinical characteristics, and perinatal outcomes were collected. Comparisons were made between patients with low- (modified World Health Organization Class I) and moderate to high–risk (modified World Health Organization Class II–IV) cardiac disease using chi-square, Fisher exact, or Student t-tests. Cohen d tests were used to estimate the effect size between group means. Logistic regression models were used to evaluate the odds of vaginal and cesarean delivery in low- and moderate to high–risk groups.

RESULTS:

A total of 108 participants were eligible for inclusion, with 41 participants in the low-risk cardiac group and 67 in the moderate to high–risk group. Participants had a mean age of 32.1 (±5.5) years at the time of delivery and a mean pregravid body mass index of 29.9 (±7.8) kg/m². Chronic hypertension (13.9%) and a history of hypertensive disorder of pregnancy (14.9%) were the most common comorbid medical conditions. In total, 17.1% of the sample had a history of a cardiac event (eg, arrhythmia, heart failure, myocardial infarction). Rates of vaginal and cesarean deliveries were similar between the low- and moderate to high–risk cardiac groups. Patients in the moderate to high–risk cardiac group were more likely to be admitted to the intensive care unit during pregnancy (odds ratio, 7.8; P<.05) and experience severe maternal morbidity compared with patients in the low-risk cardiac group (P<.01). Mode of delivery was not associated with severe maternal morbidity in the higher-risk cardiac group (odds ratio, 3.2; P=.12). In addition, infants of mothers with higher-risk disease were more likely to be admitted to the neonatal intensive care unit (odds ratio, 3.6; P=.06) and have longer neonatal intensive care unit stays (P=.005).

CONCLUSION:

There was no difference in mode of delivery by modified World Health Organization cardiac classification, and mode of delivery was not associated with risk of severe maternal morbidity. Despite the overall increased risk of morbidity in the higher-risk group, vaginal delivery should be considered as an option for certain patients with well-compensated cardiac disease. However, larger studies are needed to confirm these findings.

Introduction

Maternal morbidity and mortality in pregnancy are increasing, with cardiac disease being the leading indirect cause of mortality.^1,2 Cardiovascular conditions are responsible for more than one-third of pregnancy-related deaths, yet nearly 30% of maternal cardiac deaths may be preventable.^3,4 This may be because of several factors, including the inherent difficulty in distinguishing cardiac symptoms from those of normal pregnancy.^4,5 As treatments and life expectancy improve for patients with heart disease, the number of patients with congenital and acquired heart disease reaching childbearing age and becoming pregnant is increasing.⁶

Mode of delivery is an important consideration for obstetrical patients with cardiovascular disease and may influence maternal and neonatal outcomes. According to the American Heart Association, management of pregnant patients with complex heart disease should prioritize vaginal delivery as long as the patient is clinically stable, whereas cesarean delivery should be reserved for obstetrical indications (eg, abnormal fetal heart tracing, fetal malpresentation).⁷ This recommendation does not include patients with Marfan syndrome and aortic dilation ≥40 mm, patients with bicuspid aortic valve and aortic dilation ≥45 mm, patients with maternal or fetal instability, or patients with acute heart failure, for whom cesarean delivery is recommended.^5,8,9 Although guidelines indicate that cesarean delivery is reserved for obstetrical indications in most patients with cardiac disease, rates of cesarean delivery in obstetrical patients with cardiovascular disease are higher than those in the general population.^10–13 Cesarean deliveries are associated with increased blood loss, postpartum pain, infections, longer recovery, and greater risk of potential implications for future pregnancies (eg, placenta accreta spectrum) compared with vaginal deliveries.^14,15 In addition, the rapid autotransfusion of blood during cesarean delivery may impose additional stress on the cardiovascular system, precipitating worsening cardiac function in those with heart disease.¹⁶

Rates of vaginal and cesarean deliveries in patients with cardiac disease and the influence of modified World Health Organization (mWHO) cardiac classification on perinatal outcomes are a growing area of research. Therefore, the aim of this study was to evaluate mode of delivery, including vaginal vs cesarean delivery, among obstetrical patients with low- and moderate to high–risk cardiac disease.

Methods

Study population and design

This was a retrospective cohort study of obstetrical patients with cardiac disease, as defined by the mWHO classification of maternal cardiovascular risk, who received a perinatal echocardiogram as part of their pregnancy care. Inclusion criteria comprised obstetrical patients aged ≥18 years who: (1) received prenatal and postpartum care at a single academic, tertiary care center between October 1, 2017 and May 1, 2022, (2) had a diagnosis of cardiovascular disease before or during pregnancy, and (3) had an echocardiogram during pregnancy or within 12 weeks postpartum. Patients were excluded if medical records/echocardiograms were not available for review, or if echocardiogram(s) were only performed before pregnancy or >12 weeks after delivery. Patients who did not have echocardiogram data available for review were excluded to ensure accurate classification of maternal cardiac risk across the sample. Patients with cardiac conditions in which cesarean delivery is recommended (eg, patients with dilated aortopathy due to Marfan syndrome) were not excluded from the study because they represent an important cohort of patients with mWHO lesions and comprise a large portion of mWHO Class IV. For patients with multiple pregnancies during the 5-year eligibility period, only the first pregnancy was used.

Data were extracted from medical records between May and August 2022. A query was performed by a biostatistician to identify patients with a cardiac diagnosis who received an echocardiogram as part of their obstetrical care. Once this query was performed, trained research assistants confirmed patient eligibility on the basis of the above criteria. Data were extracted from eligible patients’ medical records and transferred to REDCap (Vanderbilt University, Nashville, TN),¹⁷ a secure database. All methods were approved by the university’s institutional review board.

Assessment of exposures and maternal outcomes

Patient demographics included age at delivery, race, ethnicity, parity, substance use in pregnancy, body mass index (BMI), history of chronic hypertension and diabetes mellitus, and history of a cardiac event, which included a history of maternal cardiac arrest, arrhythmia, heart failure, stroke/transient ischemic attack (TIA), myocardial infarction, dissection, or cardiac thromboembolism. The use of cardiac medications at the initial prenatal visit was evaluated, including diuretics, calcium channel blockers, beta-blockers or antiarrhythmic drugs, and anticoagulants.

The primary outcome of interest was mode of delivery, which included vaginal and cesarean delivery. Operative vaginal deliveries, including vacuum and forceps extraction, were included with vaginal deliveries. Gestational age at delivery was also evaluated. Indications for cesarean delivery were assessed, such as nonreassuring fetal heart tracing (NRFHT), fetal position (eg, breech), or repeated cesarean delivery. Repeated cesarean deliveries were considered elective. Cesarean deliveries for maternal indications (eg, maternal hemodynamic instability, Marfan syndrome with aortic dilation ≥40 mm, bicuspid aortic valve with aortic dilation ≥45 mm, acute heart failure, or heart failure with residual impairment) were identified and compared between groups. The annual rates of vaginal and cesarean deliveries at the study institution (from January 1, 2022 to January 1, 2023) were also obtained.

The primary exposure of interest was mWHO cardiac classification.⁹ Given the small sample size and the low incidence of predefined mWHO cardiovascular disease among obstetrical patients, the sample was stratified into 2 categories: those defined as low-risk (mWHO I) and those defined as moderate to high–risk (mWHO II, II/III, III, and IV). This allowed for comparison of mode of delivery and perinatal outcomes between diagnoses included in mWHO Class I, which is associated with a lower risk of morbidity and adverse cardiac events, and those in mWHO Classes II to IV, which are associated with a moderate to high risk of maternal morbidity and adverse cardiac events.⁵ Individuals who had >1 cardiac diagnosis in different mWHO categories were assigned to a cohort according to the more severe diagnosis. Echocardiogram data were collected and used to confirm cardiac diagnoses. Echocardiograms were considered abnormal if there was any evidence of repaired congenital heart disease, diastolic or systolic dysfunction, valvular disease, or other structural abnormalities. Rates of abnormal echocardiograms were compared between groups.

The presence of high-risk cardiac features in the current pregnancy was evaluated as a composite and included any of the following: New York Heart Association Functional Class III or IV, oxygen saturation <90% at baseline, systemic ejection fraction <40%, left ventricular outflow tract peak gradient >30 mm Hg, or an aortic condition associated with connective tissue disease.

Additional covariates of interest included gestational hypertension and preeclampsia. Gestational hypertension was defined as a systolic blood pressure of ≥140 mm Hg or a diastolic blood pressure of ≥90 mm Hg, on 2 occasions ≥4 hours apart after 20 weeks of gestation in a woman with previously normal blood pressure.¹⁸ Preeclampsia was defined as: (1) new-onset hypertension diagnosed after 20 weeks of gestation plus new-onset proteinuria (≥300 mg per 24-hour urine collection, protein/creatinine ratio of ≥0.3, or dipstick reading of 2+), or in the absence of proteinuria, (2) new-onset hypertension plus any of the following: thrombocytopenia (platelet count <100 × 10⁹/L), renal insufficiency (serum creatinine >1.1 mg/dL or a doubling of serum creatinine in the absence of other renal disease), impaired liver function (elevated blood levels of liver transaminases >2 times the upper limit of normal), pulmonary edema, or new-onset headache unresponsive to medication and not accounted for by alternative diagnoses or visual symptoms.¹⁹ Gestational diabetes mellitus was also evaluated and defined using a 2-step strategy in which plasma glucose levels are elevated following an oral glucose load according to Carpenter–Coustan critieria.^20–22

Severe maternal morbidity (SMM), as defined by the Centers for Disease Control and Prevention (CDC), was evaluated as a composite, including any maternal blood transfusion, hysterectomy, amniotic fluid embolism, air or thrombotic embolism, acute respiratory distress syndrome, severe anesthesia complication, ventilation, temporary tracheostomy, shock, sepsis, disseminated intravascular coagulation, eclampsia, cardiac arrest/ventricular fibrillation, conversion of cardiac rhythm, acute myocardial infarction, heart failure/cardiac arrest during surgery/procedure, pulmonary edema/acute heart failure, aneurysm, cerebrovascular disorders, acute renal failure, or sickle cell disease with crisis.²³ Maternal intensive care unit (ICU) admission during pregnancy or following delivery, and the length of ICU admission were also assessed.

Rates of maternal hospital readmission for a cardiac indication and the length of hospital readmission following delivery were compared between groups. This included readmission for hypertension, heart failure, arrhythmia, stroke/TIA, myocardial infarction, ischemia, angina, or maternal symptoms such as shortness of breath or syncope.

Assessment of neonatal outcomes

Neonatal outcomes of interest included fetal demise,²⁴ fetal growth restriction, defined as an estimated fetal weight or abdominal circumference that is <10th percentile for gestational age,²⁵ neonatal intensive care unit (NICU) admission, length of NICU admission in days, and a composite of any adverse neonatal outcome, which comprised neonatal intubation, neonatal cooling, respiratory distress, necrotizing enterocolitis, intraventricular hemorrhage, birth trauma, and sepsis.

Statistical analysis

Data were analyzed using RStudio (Posit Software, PBC, Boston, MA). Descriptive statistics were performed to summarize the data using means (standard deviation), median (interquartile range), and raw numbers with percentages. Analyses were then performed to compare patient demographics between those with low- and moderate to high–risk cardiac disease as defined by the mWHO classification. Categorical variables were compared with chi-square and Fisher exact tests, and continuous variables were compared with Student t-tests once normal distribution was confirmed. For continuous variables, Cohen d tests were used to report the effect size (d) of mean differences between groups.²⁶ For categorical variables with >2 outcomes, multinomial logistic regression models were used to report odds ratios (ORs) and confidence intervals (CIs). Logistic regression models were used to evaluate the odds of vaginal and cesarean delivery in lowand moderate to high–risk groups. Unadjusted and adjusted ORs were obtained. Covariates used to calculate the adjusted OR included race, pregravid BMI, and history of a cardiac event.

Results

Study population

During the study period, 526 patients underwent an echocardiogram during pregnancy or within 12 weeks postpartum. Of these, 108 patients were eligible for inclusion in the study. Among the 108 patients included in the study, 38.0% were classified as mWHO Class I, 24.1% as mWHO Class II, 22.2% as mWHO Class II/III, 4.6% as mWHO Class III, and 11.1% as mWHO Class IV (Supplemental Table). When stratified by cardiovascular risk, the low-risk (mWHO I) group comprised 41 patients and the moderate to high–risk (mWHO II–IV) group comprised 67 patients. In the low-risk group, the most common cardiac diagnoses were mild mitral valve prolapse, repaired atrial septal defect, mild pulmonic stenosis, and atrial or ectopic beats. In the moderate to high–risk group, the most common diagnoses were arrhythmia, cardiomyopathy, and valvular disease such as bicuspid aortic valve.

Patient characteristics

Among the total study cohort, patients had a mean age of 32.1 (±5.5) years at the time of delivery and a mean pregravid BMI of 29.9 (±7.8) kg/m². Age at delivery was similar between groups (Table 1). Pregravid BMI was significantly higher in the moderate to high–risk group. The higher-risk group comprised a greater proportion of White non-Hispanic and Black non-Hispanic individuals. Rates of substance use were low and similar between groups. Among the total study cohort, 39.8% of participants were nulliparous, with no difference between groups.

TABLE 1.

Patient characteristics by modified World Health Organization cardiac classification

Characteristic	mWHO I (n=41)	mWHO II–IV (n=67)	P value	OR or effect size	95% CI
Mean (standard deviation) or frequency (%)
Age at delivery	31.2 (5.3)	32.6 (5.6)	.20	−0.3	−0.65 to 0.14
Prepregnancy BMI	27.3 (5.2)	31.7 (8.8)	.003	−0.6	−1.0 to −0.16
Parity
Nulliparous	19 (46.3)	24 (35.8)	.38	1.5	0.65–3.7
Race, ethnicitya
White, non-Hispanic	19 (46.3)	40 (59.7)	.02	Ref (1)	Ref (1)
Black, non-Hispanic	2 (4.9)	11 (16.4)		2.6	0.53–13.0
Asian, non-Hispanic	2 (4.9)	1 (1.5)		0.2	0.02–2.8
Hispanic	11 (26.8)	13 (19.4)		0.6	0.20–1.5
Other/multiracial	7 (17.1)	2 (3.0)		0.1	0.03–0.7
Substance use in pregnancy
Tobacco	1 (2.4)	5 (7.5)	.40	3.2	0.34–156.2
Alcoholb	0 (0)	3 (4.5)	.28	—	—
Drugs	1 (2.4)	6 (9.0)	.24	4.0	0.45–188.3
Medical history
Cardiac diagnosis	38 (92.7)	65 (97.0)	.37	2.5	0.28–31.7
Cardiac eventc	3 (7.3)	18 (26.9)	.01	4.6	1.2–26.1
Chronic hypertension	4 (9.8)	12 (17.9)	.28	2.0	0.55–9.2
Diabetes mellitus	1 (2.4)	10 (14.9)	.05	6.9	0.92–311.6
HDP	3 (7.3)	15 (22.4)	.06	3.6	0.93–20.8
SLE	2 (4.9)	0 (0)	.14	0.0	0.0–3.2
CKD	1 (2.4)	1 (1.5)	1.0	0.6	0.01–48.8
Initial prenatal visit
On cardiac medication(s) at initial prenatal visit	5 (12.2)	17 (25.4)	.13	2.5	0.78–9.4
Mean SBP at initial prenatal visit	113.3 (9.6)	114.5 (11.7)	.58	−0.1	−0.51 to 0.29
Mean DBP at initial prenatal visit	70.6 (8.4)	69.8 (8.3)	.67	0.1	−0.31 to 0.49

BMI, body mass index; CI, confidence interval; CKD, chronic kidney disease; DBP, diastolic blood pressure; HDP, hypertensive disorder of pregnancy; mWHO, modified World Health Organization classification; OR, odds ratio; Ref, reference; SBP, systolic blood pressure; SLE, systemic lupus erythematosus.

^aWhite non-Hispanic used as reference value (1)

^bOR was not calculated given zero value for outcome of interest

^cHistory of a cardiac event comprised a history of maternal cardiac arrest, arrhythmia, heart failure, stroke/transient ischemic attack, myocardial infarction, dissection, and cardiac thromboembolism.

In total, 95.4% of participants had a prepregnancy cardiac diagnosis, whereas the remaining 4.6% were diagnosed during this pregnancy. Of the participants diagnosed with a cardiac condition in this pregnancy, 3 were mWHO Class I, 1 was mWHO Class II, and 1 was mWHO Class III. Patients in the higher-risk group were more likely to have a history of a cardiac event (P=.01), which was driven by the increased prevalence of previous heart failure in this group (P<.05). There were no differences in the history of chronic hypertension, gestational diabetes mellitus, pregestational diabetes mellitus, hypertensive disorders of pregnancy, chronic kidney disease, or systemic lupus erythematosus between groups (Table 1).

Approximately 20% of participants reported using a cardiac medication at the initial prenatal visit, with no difference in the rates of medication use between groups (Table 1). The use of beta-blockers was more common in the higher-risk group, although this difference was not statistically significant. Mean blood pressures at initial prenatal visits were similar between groups.

Echocardiograms in pregnancy

Participants had at least 1 echocardiogram as part of their prenatal or early postpartum care. A total of 28 participants had 2 echocardiograms, and 9 participants had 3. In the third trimester, 51.9% of patients completed their first echocardiogram, and 12.0% completed their first echocardiogram during the postpartum period. Participants in the moderate to high–risk group were more likely to have an abnormal echocardiogram in pregnancy (P<.05) (Table 2). Furthermore, high-risk cardiac features in the current pregnancy, comprising primarily the presence of an aortic condition associated with a connective tissue disease and systemic ejection fraction <40%, were more common in the higher-risk group (P<.05) (Table 2).

TABLE 2.

Maternal outcomes by modified World Health Organization cardiac classification

Obstetrical outcome	mWHO I (n=41)	mWHO II–IV (n=67)	P value	OR or effect Size	95% CI
Mean (standard deviation) or frequency (%)
Mode of delivery
Vaginala	26 (63.4)	36 (53.7)	.43	1.5	0.6–3.6
Cesarean	15 (36.6)	31 (46.3)
Delivery characteristics
CD for maternal indicationb,c	0 (0)	9 (13.4)	.013	—	—
CD for NRFHT	8 (19.5)	10 (14.9)	.60	0.7	0.2–2.3
Repeated CD	5 (12.2)	11 (16.4)	.80	1.4	0.4–5.6
Gestational age at delivery	39.2 (1.2)	37.5 (2.5)	<.0001	0.8	0.4–1.2
Mean SBP on admission for delivery	124.1 (16.1)	126.5 (16.4)	.47	−0.1	−0.6 to 0.3
Mean DBP on admission for delivery	75.5 (11.5)	79.0 (11.5)	.14	−0.3	−0.7 to 0.1
Pregnancy complications
High-risk cardiac feature(s)c,d	0 (0)	12 (17.9)	.003	—	—
Abnormal echocardiograme	15 (36.6)	40 (59.7)	.017	2.9	1.2–7.2
Composite SMMc	0 (0)	13 (19.4)	.002	—	—
Maternal ICU admission	1 (2.4)	11 (16.4)	.03	7.8	1.1–345.9
Gestational diabetes mellitus	5 (12.2)	9 (13.4)	1	1.1	0.3–4.6
Hypertensive disorder of pregnancy	9 (22.0)	23 (34.3)	.25	1.9	0.7–5.2
Postpartum readmissions
Readmission for cardiac reason	2 (4.9)	3 (4.5)	1	0.9	0.1–11.4
Average length of cardiac readmission	1 (0)	8.3 (10.2)	.34	−0.9	−3.9 to 2.2

CI, confidence interval; CD, cesarean delivery; DBP, diastolic blood pressure; ICU, intensive care unit; mWHO, modified World Health Organization classification; NRFHT, nonreassuring fetal heart tracing; OR, odds ratio; SBP, systolic blood pressure; SMM, severe maternal morbidity.

^aVaginal delivery including operative vaginal deliveries

^bMaternal indications for CD included maternal hemodynamic instability, Marfan syndrome with aortic dilation ≥40 mm, bicuspid aortic valve with aortic dilation ≥45 mm, acute heart failure, or heart failure with residual impairment

^cOR was not calculated given zero value for outcome of interest

^dHigh-risk cardiac features evaluated as a composite and included New York Heart Association Functional Class III or IV, oxygen saturation <90% at baseline, systemic ejection fraction <40%, left ventricular outflow tract peak gradient >30 mm Hg, or an aortic condition associated with connective tissue disease

^eEchocardiograms defined as abnormal if there was evidence of diastolic or systolic dysfunction, valvular disease, evidence of repaired congenital heart disease, or other structural abnormalities.

Mode of delivery

Rates of vaginal and cesarean deliveries were similar between groups, with 36.6% of patients in the low-risk group and 46.3% in the moderate to high–risk group having a cesarean delivery (Table 2). In the adjusted logistic regression, there was no difference in the odds of cesarean delivery between groups when adjusting for race, pregravid BMI, and history of cardiac events (Table 3). Overall, there are 4632 deliveries annually at the study institution, with 66.8% being vaginal and 34.4% being cesarean deliveries.

TABLE 3.

Logistic regression model for mode of delivery by modified World Health Organization cardiac classification

Odds of cesarean delivery	Unadjusted odds ratio (95% CI)	Adjusted odds ratio (95% CI)
mWHO II–IV	1.47 (0.67–3.23)	1.30 (0.53–3.21)
mWHOI	Reference (1.0)	Reference (1.0)

Odds ratios were adjusted for race, pregravid body mass index, and history of a cardiac event.

CI, confidence interval; mWHO, modified World Health Organization classification.

Maternal outcomes

Patients in the higher-risk group were more likely to experience SMM compared with patients in the low-risk group (P<.01), with no participants in the low-risk group experiencing SMM. The most common SMMs among the study cohort were heart failure or cardiac arrest during a surgery/procedure (23.1%) and pulmonary edema/acute heart failure (30.8%). In addition, patients in the higher-risk group were more likely to be admitted to the ICU during pregnancy or the postpartum period (Table 2). Mean ICU admission length for those in the moderate to high–risk group was 3 days with the range being 1 to 12 days. Among patients in the higher-risk group, the mode of delivery was not associated with SMM (OR, 3.2; 95% CI, 0.78–16.1; P=.12).

Participants in the higher-risk group were more likely to deliver at an earlier gestational age (P<.0001), and have a cesarean delivery for a maternal indication (Table 2). Among participants who had a cesarean delivery for a maternal indication, 44% were mWHO Class IV, 22% had aortic root dilation >40 mm associated with Marfan syndrome, and 33% had previous cardiomyopathy with residual impairment, including regional or global hypokinesis. The rates of cesarean delivery for NRFHT and repeated cesarean delivery were similar between groups.

Cardiac readmission

The rates of postpartum hospital readmission for a cardiac indication were similar between groups (Table 2). There was a trend toward having a longer readmission in the higher-risk group, although this difference was not significant. Mean length of cardiac readmission for the low-risk group was 1 day, whereas the mean length of cardiac readmission for the higher-risk group was 8.3 days. Frequent reasons for readmission included heart failure, hypertension, shortness of breath, and syncope. Readmission indications were similar between groups.

Neonatal outcomes

Among the total study cohort, there was 1 case of a fetal demise in the higher-risk group. The etiology of this fetal demise was unknown. No participants in the low-risk group experienced neonatal adverse outcomes. Six participants in the higher-risk group experienced neonatal adverse outcomes, 5 of which were respiratory distress (Table 4). NICU admission rates were similar between groups, although the average NICU admission length in days was significantly greater in the higher-risk group (d=−1.1; 95% CI, −2.9 to 0.6; P<.01).

TABLE 4.

Neonatal outcomes by modified World Health Organization cardiac classification

Neonatal outcome	mWHO I (n=41)	mWHO II–IV (n=67)	P value	OR or effect size	95% CI
Mean (standard deviation) or frequency (%)
Fetal growth restriction	1 (2.4)	5 (7.5)	.40	3.2	0.3–158.8
Composite neonatal adverse outcomea	0 (0)	6 (9.0)	.08	—	—
NICU admission	3 (7.3)	15 (22.4)	.06	3.6	0.9–20.8
NICU admission length (d)	4 (0)	21.7 (16.4)	.005	−1.1	−2.9 to 0.6

CI, confidence interval; mWHO, modified World Health Organization classification; NICU, neonatal intensive care unit; OR, odds ratio.

^aOR was not calculated given zero value for outcome of interest.

Discussion

Principal findings

In this retrospective cohort study, obstetrical patients with low-risk and moderate to high–risk cardiac disease in pregnancy, as defined by the mWHO classification of maternal cardiovascular risk, had similar rates of vaginal and cesarean deliveries. Patients in the higher-risk group were more likely to have a cesarean delivery for a maternal indication, which was not unexpected given the cardiac pathologies included in this group. Patients with higher-risk cardiac disease were also more likely to experience SMM, regardless of mode of delivery, and be admitted to the ICU during pregnancy or postpartum.

Results

Our findings that patients with moderate to high–risk cardiac disease had similar rates of cesarean delivery compared with patients with low-risk disease differ from those of previous studies. A large study by Denoble et al²⁷ found that patients with increasing severity of cardiac disease were more likely to have a cesarean delivery. However, this study compared mWHO Class I to II patients with mWHO Class II/III to IV patients. Other studies evaluating mode of delivery in patients with congenital heart disease have shown that cesarean delivery rates increase among patients with increasing severity of heart disease.^28,29

We found that patients with moderate to high–risk cardiac disease were more likely to deliver at an earlier gestational age, experience SMM, and be admitted to the ICU compared with patients with low-risk cardiac disease. Nearly 20% of patients with moderate to high–risk cardiac disease experienced SMM, and 16% of patients with higher-risk cardiac disease were admitted to the ICU during pregnancy or postpartum. These findings are consistent with previous literature demonstrating that patients with higher-risk cardiac disease are more likely to experience SMM and adverse neonatal outcomes.^27,29,30 Interestingly, in patients with moderate to high–risk cardiac disease, the mode of delivery was not associated with SMM. This is consistent with previous studies showing that cesarean delivery does not reduce adverse outcomes in patients with cardiac disease.³¹

Clinical implications

These findings suggest that vaginal delivery is a reasonable option for mode of delivery in patients with well-compensated cardiac disease, although cesarean delivery remains advised in patients with aortic dilation in the setting of Marfan syndrome or bicuspid aortic valve per the American College of Obstetricians and Gynecologists guidelines.⁵ Obstetrical providers should be aware that mode of delivery may not influence a patient’s risk of experiencing SMM, although cardiac disease does influence this risk. Therefore, vaginal birth, where it is not contraindicated for an obstetrical indication, is a reasonable option for patients with well-compensated cardiac disease.

Research implications

Future studies should seek to elucidate the impact of mode of delivery and specific cardiac lesions on maternal morbidity and perinatal outcomes. Interventions during delivery such as induction of labor or use of certain medications and how these influence outcomes may also be assessed. Future studies should also clarify how specific cardiac lesions or increasing severity of cardiac disease may influence cardiac readmission following delivery, and during what time frame in the postpartum period patients are at the greatest risk of adverse events.

Strengths and limitations

The strengths of this study include the use of the mWHO classification of maternal cardiovascular risk and the CDC’s standardized definition of SMM to evaluate outcomes. In addition, the use of echocardiogram data enabled confirmation of cardiac diagnoses across the sample and evaluation of adverse cardiac outcomes such as cardiomyopathy. Assessment of patient outcomes was limited to pregnancy and a maximum of 12 weeks postpartum. This allowed for the evaluation of cardiac readmissions in the postpartum period.

This study had several limitations, such as the small sample size, which may have limited the ability to detect differences between groups. In addition, given that no a priori sample size calculation was performed, the study may have been underpowered to detect true differences in primary outcomes. There were very few participants in mWHO Classes III to IV, which may have minimized the differences in outcomes between groups. This study was performed at a single academic medical institution, thereby affecting the data available for review and the generalizability of the results. Given that participants were divided into 2 groups based on mWHO Class, the effect of specific cardiac pathologies on mode of delivery and perinatal outcomes could not be assessed. This would provide valuable information about how specific cardiac lesions might influence maternal health during pregnancy or postpartum.

Conclusions

Although this study had a small sample size, the information presented herein, in conjunction with previous and future research, may be helpful to providers when counseling their patients with low- and moderate to high–risk cardiac disease in pregnancy. Importantly, vaginal delivery seems to be a reasonable option for certain patients with cardiac disease. In patients with well-compensated high-risk cardiac disease, mode of delivery does not seem to affect the likelihood of experiencing SMM. Further studies are needed to corroborate these findings.

AJOG MFM at a Glance.

Why was this study conducted?

Mode of delivery among patients with cardiac disease and the influence of the modified World Health Organization (mWHO) classification of maternal cardiovascular risk on perinatal outcomes is a growing area of research.

Key findings

In this retrospective cohort study comparing patients with low- (mWHO Class I) and moderate to high–risk (mWHO Class II–IV) cardiac disease, rates of vaginal and cesarean deliveries were similar between groups. Patients in the higher-risk group were more likely to experience severe maternal morbidity (SMM), although mode of delivery was not associated with risk of SMM.

What does this add to what is known?

This study adds to a growing body of data demonstrating that vaginal delivery is a reasonable option for mode of delivery in certain patients with well-compensated cardiac disease in pregnancy, and that cesarean delivery does not decrease the risk of adverse outcomes. These data corroborate the mWHO classification of maternal cardiovascular risk. Cesarean delivery should be reserved for obstetrical indications alone in patients with well-compensated cardiac disease.

Glossary

mWHO

Modified World Health Organization Classification of Maternal Cardiovascular Risk

CDC

Centers for Disease Control and Prevention

SMM

Severe Maternal Morbidity

OR

Odds Ratio

CI

Confidence Interval d = Cohen’s d effect size

BMI

Body Mass Index

HDP

Hypertensive Disorder of Pregnancy

ICU

Intensive Care Unit

NICU

Neonatal Intensive Care Unit

NRFHT

Nonreassuring Fetal Heart Tracing

SLE

Systemic Lupus Erythematosus

CKD

Chronic Kidney Disease

SBP

Systolic Blood Pressure

DBP

Diastolic Blood Pressure