From the Guidelines
Yes, it is normal to have an elevated resting heart rate during the third trimester of pregnancy, with an increase of 10-20 beats per minute above the pre-pregnancy baseline. During pregnancy, your heart rate typically increases to support the expanded blood volume, which is approximately 40-50% higher than pre-pregnancy levels, as noted in the study by 1. This increase in heart rate helps to ensure adequate blood flow to the placenta and supports the increased metabolic demands of pregnancy.
Key Points to Consider
- The elevated heart rate is a normal physiological change during pregnancy, particularly in the third trimester, as stated in the study by 1.
- Other factors that can further increase heart rate during the third trimester include physical activity, stress, dehydration, and anemia.
- While this elevation is normal, if you experience a sudden, significant increase in heart rate accompanied by shortness of breath, chest pain, dizziness, or fainting, you should contact your healthcare provider immediately as these could indicate a more serious condition requiring medical attention.
Physiological Changes During Pregnancy
The study by 1 highlights the changes in the cardiovascular system during pregnancy, including increases in blood volume and cardiac output, and reductions in systemic vascular resistance and blood pressure.
- The heart rate starts to rise at 20 weeks and increases until 32 weeks, remaining high 2-5 days after delivery.
- Systemic blood pressure typically falls early in gestation and diastolic blood pressure is usually 10 mmHg below baseline in the second trimester.
Clinical Implications
It is essential to distinguish between normal physiological changes and potential pathological conditions, as emphasized in the study by 1.
- Echocardiography is recommended in pregnant patients with unexplained or new cardiovascular signs or symptoms.
- Cardiovascular magnetic resonance (without gadolinium) should be carried out if additional information is required. By understanding these physiological changes and clinical implications, healthcare providers can better manage pregnant patients and ensure the best possible outcomes for both mother and baby.
From the Research
Elevated Resting Heart Rate in 3rd Trimester
- There is no direct evidence in the provided studies to suggest that an elevated resting heart rate is normal in the 3rd trimester of pregnancy 2, 3.
- The studies primarily focus on complications that can arise during the second and third trimesters, such as hemorrhage, infection, and hypertensive diseases of pregnancy 2, and challenges related to preterm labor, hypertensive disorders, and bleeding events 3.
- None of the studies specifically address the normal range of resting heart rate during the 3rd trimester or its potential elevation.
- Studies 4, 5, 6 discuss the use of beta-blockers for treating arrhythmias and their effects on heart rate, but these are not directly related to normal heart rate variations during pregnancy.
Related Heart Rate Studies
- A study on beta-blockers for arrhythmias discusses their pharmacokinetic and pharmacodynamic properties, but does not address normal heart rate in pregnancy 4.
- Another study examines the outcomes of patients with catecholaminergic polymorphic ventricular tachycardia treated with β-blockers, which is not relevant to normal heart rate in pregnancy 5.
- A systematic review and meta-analysis on beta-blockade for cardiac arrest due to ventricular fibrillation or pulseless ventricular tachycardia also does not provide information on normal heart rate in pregnancy 6.