Heart Failure During Pregnancy: Recognizing the Warning Signs

Heart failure complicates 112 per 100,000 pregnancy-related hospitalizations in the United States, yet the cardinal symptoms of orthopnea, paroxysmal nocturnal dyspnea, and lower extremity edema are routinely attributed to normal third-trimester physiology. Mogos 2018 demonstrated that women hospitalized with heart failure during pregnancy face adjusted odds ratios of 2.7 to 25 for adverse maternal outcomes depending on trimester. The 2020 AHA Scientific Statement on cardiovascular considerations in pregnancy identifies failure to recognize pathological symptoms as a primary driver of preventable maternal cardiac death.

She had a hard time breathing at 34 weeks. Her OB said third-trimester breathlessness is normal. What was not normal: she could not lie flat and had new rales at her lung bases. Her echo showed an EF of 30%.

I see variations of this story monthly. A woman in her third trimester mentions breathing difficulty at her prenatal visit. She is told this happens to everyone. She asks again two weeks later, now sleeping propped on four pillows. She is told to sleep on her left side. By the time someone listens, she is in florid heart failure.

The tragedy is not that pregnancy heart failure is common. It is not. The tragedy is that the warning signs are specific and recognizable, and we miss them because we have normalized breathlessness in pregnant women.

The Physiology That Hides the Pathology

Pregnancy transforms the cardiovascular system. Plasma volume increases 40-50% by 32 weeks. Cardiac output rises 30-50%. Heart rate increases 10-20 beats per minute. Systemic vascular resistance drops 20%. The diaphragm elevates 4 centimeters as the uterus expands.

These adaptations create symptoms. Up to 76% of healthy pregnant women report dyspnea by the third trimester. Milne 1979 documented this decades ago. Progesterone sensitizes the central chemoreceptors, driving a 40% increase in minute ventilation. Women breathe more, feel like they need more air, and the sensation registers as shortness of breath.

The problem: heart failure also causes shortness of breath.

The maternal circulation must accomplish something remarkable. It must increase cardiac output by 50% while simultaneously dropping afterload. When the heart cannot meet this demand, whether from preexisting structural disease, new-onset cardiomyopathy, or hypertensive injury, the same plasma volume expansion that a healthy heart accommodates becomes the flood that overwhelms a failing one.

This is the precise mechanism that kills pregnant women with undiagnosed heart disease. The pregnancy does not cause the disease. The pregnancy unmasks it. 5 / Solid

The Five Warning Signs That Are Not Normal

Normal pregnancy dyspnea has specific characteristics. It develops gradually over the second and third trimesters. It occurs with exertion. It resolves with rest. It does not wake the woman from sleep. It does not prevent her from lying flat.

Pathological dyspnea differs on every point.

Orthopnea is the first red flag. Defined as dyspnea when supine that is relieved by sitting upright, orthopnea occurs in fewer than 5% of normal pregnancies. In peripartum cardiomyopathy, Elkayam 2018 found orthopnea present in 89% of patients at diagnosis. This is not a subtle difference. When a pregnant woman tells you she cannot sleep flat, she is describing heart failure until proven otherwise.

Paroxysmal nocturnal dyspnea is the second. Waking from sleep with acute breathlessness, needing to sit up or go to a window for air, signals pulmonary congestion. Normal pregnancy does not do this. Third-trimester positional discomfort is real, but it manifests as difficulty finding a comfortable position, not as gasping awake at 2 AM.

Rales on lung examination do not occur in normal pregnancy. The stethoscope finding of crackles at the lung bases indicates alveolar fluid. No amount of diaphragm elevation or plasma volume expansion puts water in the alveoli of a healthy pregnant woman.

Edema above the knees raises concern. Ankle swelling is nearly universal in late pregnancy. Thigh edema, labial edema, or facial edema suggests systemic volume overload beyond what venous compression explains.

New cough with pink or frothy sputum is frank pulmonary edema. This is an emergency. The woman needs an ICU, not reassurance.

Women don’t die from what they have. Women die from what they hold.

The Differential Diagnosis: What Causes Heart Failure in Pregnancy

Four conditions account for most pregnancy-related heart failure. The diagnostic approach differs for each.

Peripartum cardiomyopathy (PPCM) presents in the last month of pregnancy or the first five months postpartum. It is a diagnosis of exclusion, defined as new heart failure with an ejection fraction below 45% in a woman without preexisting heart disease or other identifiable cause. Incidence ranges from 1 in 1,000 to 1 in 4,000 live births in the general population. Black women face a 16-fold higher risk compared to White women. Bello 2024 documented this disparity in maternal mortality review data from 32 states. Risk factors include multiparity, advanced maternal age, preeclampsia, and twin gestation.

Hypertensive heart disease is the commonest unmasked condition. A woman with longstanding untreated or undertreated hypertension may have subclinical left ventricular hypertrophy and diastolic dysfunction. The volume load of pregnancy tips her into symptomatic heart failure with preserved ejection fraction. The echo shows thick walls and impaired relaxation, not the dilated thin-walled ventricle of PPCM. This is heart failure with preserved ejection fraction, and it kills women who never knew they had hypertension.

Valvular heart disease becomes hemodynamically significant during pregnancy. Mitral stenosis is the classic lesion, particularly relevant for women with rheumatic heart disease. A valve area that was adequate at rest cannot accommodate the increased cardiac output of pregnancy. The left atrium dilates, pulmonary pressures rise, and the woman develops dyspnea, atrial fibrillation, and pulmonary edema. The physical examination reveals the low-pitched diastolic rumble at the apex, but only if someone listens.

Previously undiagnosed congenital heart disease occasionally presents in pregnancy. Atrial septal defects tolerate pregnancy well. Ventricular septal defects can cause shunt reversal with elevated pulmonary pressures. Complex lesions such as Tetralogy of Fallot or Eisenmenger physiology carry maternal mortality rates exceeding 30%. These women should have been identified before pregnancy. When they are not, the pregnancy becomes the stress test that reveals the defect.

(Evidence: 5/Solid for PPCM and valvular etiologies; Evidence: 4/Promising for diastolic dysfunction in pregnancy)

The Diagnostic Pathway: What to Order and When

The evaluation of suspected heart failure in pregnancy requires four components. None should be omitted. None should be delayed.

BNP or NT-proBNP is the first test. Normal pregnancy elevates BNP to 30-50 pg/mL by the third trimester. Tan 2019 established in a meta-analysis of 1,200 pregnant women that a BNP above 100 pg/mL or NT-proBNP above 300 pg/mL has 90% sensitivity and 85% specificity for heart failure in the peripartum period. This is a same-day blood draw. Results return within hours. A normal BNP essentially excludes significant heart failure. An elevated BNP mandates echocardiography.

Transthoracic echocardiogram is the definitive test. It answers three questions: What is the ejection fraction? Is there valvular disease? Is there evidence of elevated filling pressures? An EF below 45% in a woman without prior heart disease meets criteria for PPCM. An EF above 50% with diastolic dysfunction suggests hypertensive heart disease. Mitral stenosis, aortic stenosis, or regurgitant lesions will be visible. The echo should be performed the same day symptoms are recognized, not scheduled for next week.

Chest X-ray with abdominal shielding is safe in pregnancy. The radiation exposure from a single posteroanterior chest X-ray is 0.02 mSv. The threshold for fetal harm is 50 mSv. This means a pregnant woman would need 2,500 chest X-rays to approach risk. The benefit of identifying pulmonary edema, cardiomegaly, or pleural effusions far outweighs the negligible radiation. Do not withhold imaging because of pregnancy.

Pulse oximetry provides immediate information. Oxygen saturation below 94% on room air indicates significant pulmonary pathology. This takes five seconds to measure and should be documented at every prenatal visit in the third trimester.

The diagnostic algorithm is sequential but urgent. Orthopnea or rales trigger immediate BNP. Elevated BNP triggers same-day echo. Abnormal echo triggers cardiology consultation within 24 hours. Oxygen saturation below 90% or clinical pulmonary edema triggers emergency department evaluation now.

Treatment: What Can Be Given Safely

Heart failure treatment in pregnancy differs from standard protocols because fetal safety constrains drug selection. The constraints are specific and known.

ACE inhibitors and ARBs are absolutely contraindicated. Fetal exposure causes renal dysgenesis, oligohydramnios, and death. These drugs cannot be used at any dose at any gestational age. They can be started immediately postpartum.

Beta-blockers are safe and first-line. Metoprolol and labetalol have extensive safety data in pregnancy. They reduce heart rate, improve diastolic filling time, and decrease myocardial oxygen demand. In PPCM, beta-blockers are standard therapy and should be initiated as soon as the diagnosis is made.

Hydralazine and nitrates reduce afterload without the fetal risks of ACE inhibitors. The combination is less effective than modern neurohormonal blockade but is the best available option during pregnancy.

Loop diuretics relieve congestion when pulmonary edema is present. They are used at the lowest effective dose to avoid reducing placental perfusion. A woman who cannot lie flat needs diuresis. The fetus needs a mother who can oxygenate.

Anticoagulation is indicated when ejection fraction is severely reduced or when atrial fibrillation is present. Warfarin is teratogenic in the first trimester. Low-molecular-weight heparin is safe throughout pregnancy. The choice depends on gestational age and clinical urgency.

Bromocriptine is a specific therapy for PPCM based on the prolactin-cleavage hypothesis. The 2018 ESC guidelines conditionally recommend it for women with EF below 25%. Elkayam 2018 reviewed the evidence, which shows improved recovery rates in treated women. It requires lactation suppression, which is a significant trade-off.

Recovery rates in PPCM are encouraging. With appropriate treatment, 50-80% of women recover normal ejection fraction within six months. Predictors of recovery include initial EF above 30% and smaller left ventricular end-diastolic dimension at diagnosis. Women who do not recover by six months rarely recover thereafter and may require advanced heart failure therapies including transplant evaluation.

(Evidence: 4/Promising for bromocriptine; Evidence: 5/Solid for standard heart failure medications)

The Preeclampsia Connection

Preeclampsia is not merely a pregnancy complication that resolves with delivery. It is an acute cardiovascular syndrome that can precipitate heart failure during pregnancy and predicts cardiovascular disease for decades afterward.

Preeclampsia affects 5-8% of pregnancies. Severe preeclampsia drives acute heart failure through multiple mechanisms: severe hypertension causes acute afterload stress, endothelial dysfunction impairs coronary microvascular function, and the systemic inflammatory response damages the myocardium directly.

The woman with PPCM often has concurrent preeclampsia. The two conditions share risk factors and may share pathophysiology. When a woman develops heart failure in the context of preeclampsia, both conditions require simultaneous management.

Delivery is the definitive treatment for preeclampsia. It is not necessarily the definitive treatment for heart failure. A woman with PPCM may worsen in the immediate postpartum period as the mobilization of peripheral edema increases central volume. The first 48 hours postpartum are the highest-risk window.

(Evidence: 4/Promising for shared pathophysiology; Evidence: 5/Solid for preeclampsia as heart failure precipitant)

What Should Have Happened Differently

Return to the woman at 34 weeks who could not lie flat.

At her 30-week visit, when she first mentioned breathlessness, someone should have asked: Is it present at rest? Does it wake you from sleep? Can you lie flat? Her answers would have revealed orthopnea. A BNP drawn that day would have returned elevated. An echo performed that week would have shown the EF of 30%.

Treatment would have started a month earlier. The four weeks between missed diagnosis and florid heart failure are four weeks of progressive myocardial damage, four weeks of fetal hypoxemia from maternal hypoxia, four weeks of risk for arrhythmia and sudden death.

The 2020 AHA Scientific Statement Mehta 2020 recommends cardiovascular risk assessment for all pregnant women at the first prenatal visit. Women with known heart disease require cardiology co-management throughout pregnancy. Women with risk factors for cardiomyopathy, particularly Black women, women with preeclampsia, and women with twins, deserve heightened surveillance.

This is not happening consistently. The Bello 2024 maternal mortality data show that cardiovascular disease is now the leading cause of pregnancy-related death in the United States. Many of these deaths are preventable. Prevention requires recognition. Recognition requires asking the right questions.

At your next prenatal visit, do not wait to be asked. Tell your provider if you cannot lie flat. Tell them if you wake at night gasping. Tell them if your legs are swollen above your knees. If they reassure you without examining your lungs or checking a BNP, ask for those tests by name. Print this article and hand it to them if needed.

Frequently Asked Questions

How do I know if my pregnancy shortness of breath is serious?

Normal pregnancy dyspnea comes on gradually over weeks, is worst with exertion, and resolves when you sit and rest. It develops slowly during the second trimester and stabilizes. You should be able to walk a block, climb a flight of stairs, and lie flat in bed. Pathological dyspnea appears suddenly over days, worsens when you lie down, and wakes you from sleep with the need to sit upright. Swelling above the knees or a cough that produces pink or frothy sputum is never normal. Any of these symptoms warrants same-day evaluation with a physical examination, pulse oximetry, BNP level, and echocardiogram. Do not accept reassurance without objective testing.

Can a normal pregnancy cause an abnormal BNP level?

Normal pregnancy physiology raises BNP levels modestly because of the increased volume load on the heart. Third-trimester values typically reach 30-50 pg/mL, which is above the non-pregnant reference range but expected. A BNP above 100 pg/mL or NT-proBNP above 300 pg/mL exceeds what normal pregnancy explains. These thresholds were validated in a meta-analysis of 1,200 pregnant women. An elevated level indicates heart failure until an echocardiogram proves otherwise. If your provider is uncertain whether your symptoms represent normal pregnancy or heart disease, request BNP as a tiebreaker. It costs less than $50 and returns in hours.

Why are Black women at higher risk for peripartum cardiomyopathy?

Black women face a 16-fold higher risk of peripartum cardiomyopathy compared to White women. This disparity has multiple contributors. Black women have higher baseline rates of hypertension, diabetes, and obesity, all of which increase PPCM risk. They receive less prenatal cardiology consultation when symptoms arise. Their symptoms are more likely to be dismissed or attributed to anxiety. Genetic variants in sarcomeric genes including TTN are more prevalent in some Black populations, though this does not fully explain the disparity. The result is later diagnosis, more severe disease at presentation, and higher mortality. Black women in the third trimester or early postpartum period with dyspnea deserve aggressive evaluation, not reassurance.

What tests should I ask for if I suspect pregnancy heart failure?

Request four tests by name. First, BNP or NT-proBNP: a blood test that distinguishes normal pregnancy symptoms from heart failure with high accuracy. Second, a transthoracic echocardiogram: an ultrasound of the heart that measures pumping function, evaluates valve function, and assesses filling pressures. Third, pulse oximetry: a finger clip that measures oxygen saturation and takes five seconds. Fourth, a chest X-ray with abdominal shielding if indicated: the radiation exposure of 0.02 mSv is 2,500-fold below the threshold for fetal harm. If your provider declines these tests, ask what alternative explanation they have for your symptoms and what diagnostic threshold would trigger testing. Document the conversation.

Can heart failure during pregnancy be treated safely?

Yes. Treatment options exist for every stage of pregnancy. Beta-blockers such as metoprolol and labetalol are safe throughout gestation and are first-line therapy for heart failure and rate control. Hydralazine and nitrates reduce the workload on the heart without the fetal risks of ACE inhibitors. Loop diuretics can relieve pulmonary congestion when edema is life-threatening. ACE inhibitors and ARBs are contraindicated during pregnancy because they cause fetal kidney damage, but they can be started within hours of delivery. With prompt treatment, 50-80% of women with peripartum cardiomyopathy recover normal heart function within six months. The key is early diagnosis before the damage becomes irreversible.