What are the cardiovascular changes associated with pregnancy?

From the Guidelines

Pregnancy induces significant cardiovascular adaptations, including a 30-50% increase in cardiac output, a 40% increase in plasma volume, and a decrease in systemic vascular resistance, which can unmask or worsen underlying cardiac conditions. These changes are necessary to support the developing fetus and prepare the mother's body for delivery. According to the most recent study 1, cardiac output reaches a maximum of 40–50% above baseline by 32-weeks’ gestation, with this rise mainly driven by an increase in stroke volume, but also by a less marked and more gradual rise in heart rate.

Key Cardiovascular Changes

• Blood volume increases by 30-50% during pregnancy, with plasma volume expanding more than red cell mass, resulting in physiologic anemia
• Cardiac output rises by 30-50%, peaking in the second trimester, due to increased stroke volume and heart rate
• Systemic vascular resistance decreases by 25-30%, causing a drop in blood pressure during the first and second trimesters before returning to near-normal levels in the third trimester
• The heart undergoes structural changes, including mild ventricular hypertrophy and dilation to accommodate the increased blood volume
• Heart rate increases by 10-20 beats per minute, and the position of the heart shifts upward and leftward as the growing uterus elevates the diaphragm

Clinical Implications

• These adaptations can unmask or worsen underlying cardiac conditions, and women with cardiovascular disease are at increased risk of obstetric complications, including pre-eclampsia, pre-term delivery, and postpartum haemorrhage 1
• Pregnancy is a hypercoagulable state associated with increased risk of thromboembolism, with the highest risk for pulmonary embolism occurring immediately postpartum 1
• The European Society of Cardiology guidelines on the management of cardiovascular diseases during pregnancy provide comprehensive guidance in this area 1

Monitoring and Management

• Normal ranges for maternal vital signs are different from those of the general population, and the physiological monitoring of pregnant women requires tailored charts such as the modified early obstetric warning score 1
• The physiological changes of pregnancy should not be overestimated, as pathology might be missed, and careful monitoring and management are necessary to prevent complications and ensure the best possible outcomes for both mother and fetus 1

From the Research

Cardiovascular Changes During Pregnancy

The cardiovascular system undergoes significant changes during pregnancy, including:

• Increased maternal blood volume, heart rate, and cardiac output 2, 3, 4
• Decreased peripheral resistance and increased uteroplacental blood flow 3, 4
• Increased left ventricular dimensions, but no change in left ventricular contraction force or its first derivative 3
• A slight decrease in diastolic blood pressure, but overall arterial blood pressure remains unaffected 3

Symptoms and Findings

These cardiovascular changes can cause various symptoms and findings, such as:

• Dyspnea on exertion, presyncope, and prominent jugular venous pulsation 3
• Leg edema and ejection murmurs over the aorta and pulmonary artery 3
• Fatigue, orthopnea, and presyncope 2

Complications and Risks

Pregnancy can also increase the risk of cardiovascular complications, including:

• Hypertension, which can be transient and benign or chronic and gestational 2
• Cardiovascular disease, which can complicate 1-4% of pregnancies and is a leading cause of maternal death 5
• Acute cardiovascular events, such as heart failure, arrhythmias, coronary artery disease, and aortic and thromboembolic events 6

Management and Diagnosis

Diagnostic evaluation of pregnant women must be approached cautiously to avoid risk to the fetus, and methods using ionizing radiation should be avoided whenever possible 2. Management of cardiovascular disease in pregnancy is challenging due to the unique maternal physiology and the potential risks to the fetus 5, 6. Preconception counseling and structured follow-up during pregnancy are important measures for reducing the risk of acute cardiovascular complications 6.