Cardiovascular Changes During Pregnancy

GE Healthcare

Pregnancy involves a complex series of physiological changes, including cardiovascular ones, that are necessary to support a growing fetus. While many patients withstand those cardiovascular changes during pregnancy without complications, approximately 30% of pregnant patients do experience adversities that can affect mother and child, such as preeclampsia and gestational hypertension.1

More pregnant patients die of cardiovascular disease (CVD) than any other pregnancy-related cause of mortality—and those rates are going up. Between 1987 and 2015, for example, incidences of CVD mortality have more than doubled from 7.2 to 17.2 per 100,000 live births.2 Marginalized groups, including people of color, encounter maternal health disparities that increase their risk for these concerns.3

It's because of these and other worrying trends that the expanding field of cardio-obstetrics has emerged, combining multidisciplinary specialists in both cardiology and obstetrics to surveil patients' cardiac function and health during the preconception, prenatal, and postpartum periods.

Whether cardiologists are part of a cardio-obstetrics team or providing care independently, they should approach patients who are, recently were, or desire to be pregnant with diligent monitoring and early intervention. Fortunately, many guidance documents from the American Heart Association, American College of Obstetrics and Gynecology, European Society of Cardiology, and others are available to help navigate that care. 2,3,4

Here we'll discuss several highlights from that guidance that every practitioner working with these patient populations should know.

Expected Cardiovascular Changes During Pregnancy

The physical demands of pregnancy require bodily changes that include increased cardiac output, heart rate, and blood volume, as well as reductions in blood pressure and systemic vascular resistance.5 Normal cardiac and hematologic changes seen during pregnancy are generally marked by these measures:

  • Cardiac output tends to rise about 30 to 50%, with increases starting in the first trimester and reaching their height between 16 and 28 weeks. After that point, cardiac output stays around those high levels until a slight reduction at 30 weeks. During labor, output rises an additional 30% and falls to a 15-to-25% elevation after delivery. By six weeks postpartum, output returns to normal levels.5
  • Heart rate will rise throughout pregnancy, with the most pronounced increases of 15% to 20% in the third trimester. During labor, pulse surges 40% to 50% with contractions.3
  • Blood volume will fluctuate up and down in parallel with cardiac output, with a more pronounced increase in plasma volume compared to the volume of red blood cell mass.5
  • Blood pressure will typically decrease in the first trimester (down 10%) and second trimester (down 5%), with a slight 5% increase in the third trimester. Readings will elevate during labor, fluctuate slightly after delivery, and return to normal in postpartum.3
  • Vascular resistance typically falls roughly 30% from pre-pregnancy until the second trimester, after which it increases slightly until recovering to normal levels in early postpartum.2

Cardiovascular Concerns During Pregnancy

Even though many women will tolerate the normal physiological changes of pregnancy without circumstance, some cardiac concerns can occur—often, but not always, in patients with a preexisting cardiovascular history or a previous pregnancy with a complication.

Hypertension and Preeclampsia

Hypertension is common and can range in severity, with less serious instances (particularly those identified early in pregnancy) being well managed with medication. However, sudden hypertension with protein in urine after 20 weeks is classified as preeclampsia, which can significantly increase risk of death, coronary artery disease, and heart failure.2

Recently, research has observed an effect between prenatal supplements containing high doses of folic acid (800 mcg or more) and an increased risk of hypertension, but not preeclampsia. While more research is needed, these links should be understood by clinicians when moderate-dose options of 400 mcg may be available.6

Ischemic Heart Disease

Pregnant patients face a significantly higher risk (up to four-fold) of acute myocardial infarction than nonpregnant patients, even though incidences are very low, with roughly 2.8 to 8.1 cases per 100,000 births.2 This risk is highest during the third trimester and postpartum period.

High-risk individuals include those with a history of coronary artery disease. Patients in these populations encounter a 10% chance of experiencing ischemic complications during pregnancy.2

Arrhythmias and Heart Palpitations

Even though they're generally harmless and widely understood as a common sign of pregnancy, suspected palpitations or arrhythmias during pregnancy should always be evaluated by the medical team.3

This is due to the risk of underlying structural heart disease, including peripartum cardiomyopathy in the final weeks of pregnancy and up to five months postpartum.7 Generally, palpitations associated with atrial and ventricular ectopy, as well as sinus tachycardia, are not a cause for concern. More complex arrhythmias, including supraventricular tachycardia and wide-complex tachyarrhythmias, may require treatment.2

Thrombosis and Embolism

Risks for deep vein thrombosis (DVT) and pulmonary embolism (PE) are rare but serious, accounting for a risk of 0.3% and 1.2%, respectively. Most of these instances take place after delivery, and each can result in serious cardiovascular consequence.2 Approximately 4% of patients with venous thromboembolism have cardiac arrest.3

Other Conditions to Note

Importantly, this list of cardiac concerns is not comprehensive. Many other conditions, including hypercholesterolemia, valvular heart disease, aortic disease, cerebrovascular disease, and others, may warrant continued surveillance and early intervention, particularly for high-risk patients.2

Should At-Risk Patients Become Pregnant?

Many women can achieve positive pregnancy outcomes, even with preexisting cardiovascular histories or other risk factors.4 Preconception counseling is critical for these patients, who will also need care from a cardio-obstetric team.2 Risk assessments will typically include ECG, echocardiography, and exercise testing—with more advanced diagnostics such as imaging for aortic disease.3

Ideally, patients should aim to have the most optimal cardiovascular health possible before conceiving. To accomplish this, they might need to manage their weight, stop smoking, and follow a healthy diet.3


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Monitoring & Diagnosis

Routine prenatal care for all patients includes regular blood pressure monitoring and laboratory work. Beyond this standard care, however, patients should be evaluated if suspected or known problems such as palpitations, chest pain, or medical history raise concerns. Depending on the concern, diagnostic plans may include troponin testing, ECG, echocardiography, exercise stress tests, CT, MRI, or other methods.3

After pregnancy, monitoring of patients with CVD may be necessary to manage the risk of future or sustained cardiac problems associated with hormonal contraception, subsequent pregnancies, and other postpartum risks.2

Managing Care During Preconception, Pregnancy, and Postpartum

Pregnancy can represent a vulnerable time for patients, with both physical and mental changes coalescing into what—in any other time—could become significant risk factors for cardiovascular disease. Additionally, pregnancy symptoms can disguise or delay serious underlying problems, given the amount and extent of physical discomforts associated with this stage of life.3

For these reasons, clinicians should take care when working with patients who are, were, or would like to become pregnant. Diligent monitoring can help to identify and diagnose problems earlier on, and tools such as ECG can be essential to have at the bedside to protect patients from these serious complications.

References:

1. American College of Cardiology. Adverse pregnancy outcomes: a window into cardiovascular disease prevention. ACC.org. https://www.acc.org/latest-in-cardiology/articles/2020/08/31/09/40/adverse-pregnancy-outcomes. Accessed March 2, 2022.

2. Mehta LS, Warnes CA, Bradley E, et al. Cardiovascular considerations in caring for pregnant patients: a scientific statement from the American Heart Association. Circulation. 2020;141(23). https://www.ahajournals.org/doi/10.1161/CIR.0000000000000772.

3. ACOG Practice Bulletin No. 212: Pregnancy and Heart Disease. Obstetrics & Gynecology. 2019;133(5):e320-e356. https://journals.lww.com/greenjournal/Fulltext/2019/05000/ACOG_Practice_Bulletin_No__212__Pregnancy_and.40.aspx.

4. Regitz-Zagrosek V, Roos-Hesselink JW, Bauersachs J, et al. 2018 ESC Guidelines for the management of cardiovascular diseases during pregnancy. European Heart Journal. 2018;39(34):3165-3241. https://academic.oup.com/eurheartj/article/39/34/3165/5078465.

5. Artal-Mittelmark R. Physiology of pregnancy. Merck Manuals Professional Edition. https://www.merckmanuals.com/professional/gynecology-and-obstetrics/approach-to-the-pregnant-woman-and-prenatal-care/physiology-of-pregnancy. Accessed March 2, 2022.

6. American Heart Association. Prenatal supplement may increase blood pressure at high doses. www.heart.org. https://www.heart.org/en/news/2020/05/11/prenatal-supplement-may-increase-blood-pressure-at-high-doses%29. Accessed March 2, 2022.‌

7. Johns Hopkins Medicine. Peripartum cardiomyopathy. HopkinsMedicine.org. https://www.hopkinsmedicine.org/health/conditions-and-diseases/peripartum-cardiomyopathy. Accessed March 2, 2022.