By Jamie L. W. Kennedy, MD, FACC

Associate Professor, Division of Cardiology, Advanced Heart Failure & Transplant Cardiology, University of California, San Francisco

Dr. Kennedy reports no financial relationships relevant to this field of study.

SYNOPSIS: Investigators determined about half of serious cardiac complications of pregnancy are preventable.

SOURCE: Pfaller B, Sathananthan G, Grewal J, et al. Preventing complications in pregnant women with cardiac disease. J Am Coll Cardiol 2020;75:1443-1452.

Cardiovascular disease is the leading cause of maternal mortality in the United States, accounting for more than one-third of all pregnancy-related deaths.1 The rate of adverse fetal events also is much higher in women with heart disease, including premature birth, small for gestational age infants, and fetal death. Pfaller et al sought to characterize serious cardiac events in pregnant women with heart disease.

Pregnant women with heart disease were prospectively enrolled in the Canadian Cardiac Disease in Pregnancy (CARPREG) study. Some patients were known to have heart disease prior to conception, while others were diagnosed during pregnancy. This substudy concerned the cohort of patients followed at two centers, one in Vancouver and one in Toronto, between 2004 and 2014. Serious events during pregnancy and up to six months postpartum were recorded. Cardiac events included heart failure, cardiac death, arrest, arrhythmias requiring intensive care unit admission, myocardial infarction, aortic dissection, mechanical valve thrombosis, endocarditis, cerebrovascular events, and need for urgent cardiac intervention. At least two cardiologists reviewed serious cardiac events to determine preventability and contributing factors.

Of the 1,315 pregnancies followed in this study, 17% were complicated by cardiac events, 3.6% of them serious, including five maternal deaths and four resuscitated cardiac arrests. Patients with acquired heart disease, mechanical valves, high-risk native valve lesions, systemic ventricular dysfunction, cyanosis, and New York Heart Association class III or IV symptoms were more likely to suffer serious cardiac events. The need for urgent cardiovascular intervention was the most common serious cardiac event, occurring in 0.7% of pregnancies and including valve intervention, resection of cardiac tumor, atrial septal defect closure, and aortic root replacement. Two-thirds of events occurred during pregnancy: one-quarter postpartum, and the remaining during labor and delivery.

Of the 47 pregnancies complicated by severe cardiac events, 42 resulted in live births (45% were preterm deliveries). The overall rate of adverse fetal events in pregnancies with severe cardiac events was 62%, compared to 29% in pregnancies without cardiac events and 32% in pregnancies with nonserious cardiac events. There were 22 severe obstetric events, none fatal, most commonly severe pre-eclampsia. Overall, 5.1% of pregnancies were complicated by pre-eclampsia. Fortunately, only two pregnancies were complicated by both severe cardiac and obstetric events.

On chart review, 49% of severe cardiac events were considered definitely, probably, or possibly preventable, including two maternal deaths and three cardiac arrests. Most preventable events occurred in the antepartum period. Provider management-related factors were the largest group of preventable events (74%), including failure to identify cardiac disease, failure to recognize high-risk patients, delays in diagnosis and intervention, and inappropriate treatment. Many preventable events occurred in women who had not been diagnosed with heart disease and patients initially managed at smaller centers. Patient-related factors were identified in 17% of events, including failure to seek care, noncompliance, and lack of access to healthcare. The authors concluded that although uncommon, about half of serious cardiac complications of pregnancy are preventable.


The Centers for Disease Control and Prevention reports pregnancy-related mortality in the United States was 17.4 per 100,000 live births in 2018, up from 7.2 per 100,000 in 1987.2,3 In Canada, the rate has been fairly stable at between 9 and 11 deaths per 100,000 live births between 2000 and 2017.4 The reasons for the increase in the United States are many and poorly understood. More women conceiving and delivering at an older age (and more likely to do so with comorbid conditions) and improved survival to adulthood for patients with congenital heart disease are two likely contributors. Comorbid conditions in Canadian women also have increased over time without a corresponding increase in mortality, raising the possibility that the Canadian healthcare system is better equipped to care for pregnant women with heart disease.

Sadly, there are significant racial and ethnic disparities in outcomes. Black women exhibit the highest maternal mortality rate in the United States at 42.2 deaths per 100,000 live births.2 Disadvantages that black women experience at many levels contribute to this discrepancy, including the rate of unintended pregnancy, burden of comorbid conditions, and limited healthcare access. Of note, black women are more frequently affected by peripartum cardiomyopathy for unclear reasons. The reported number of serious cardiac events in this population of pregnant women with heart disease is not unexpected, although the high number of potentially preventable events is surprising. Regardless, there is an opportunity for improvement. Women with known heart disease are somewhat easier to target, with interventions such as preconception counseling, referral to an expert center, and close monitoring throughout pregnancy and the postpartum period by both obstetrician and cardiologist. Interpreting the many physiological changes of pregnancy can be challenging for both patient and physician. Serial biomarkers such as brain natriuretic peptide and even echocardiograms to monitor left ventricular function can be helpful.

Faster diagnosis of heart disease during pregnancy requires higher suspicion from treating physicians, primarily in obstetrics, primary care, and emergency medicine, followed by the cardiologists who receive these referrals. Dyspnea at rest, orthopnea, and severe chest pain always are abnormal and warrant full evaluation.


  1. Petersen EE, Davis NL, Goodman D, et al. Vital Signs: Pregnancy-related deaths, United States, 2011-2015, and strategies for prevention, 13 states, 2013-2017. MMWR Morb Mortal Wkly Rep 2019;68:423-429.
  2. National Vital Statistics Report. Maternal mortality in the United States: Changes in coding, publication, and data release, 2018. Jan. 30, 2020.
  3. Centers for Disease Control and Prevention. Pregnancy mortality surveillance system. Updated Feb. 4, 2020.
  4. World Health Organization. Maternal mortality in 2000-2017, Canada. Published 2019.