A higher heart rate is normal during pregnancy and is a necessary physiological response to the work of growing a baby. The maternal body undergoes profound, temporary changes to sustain both the mother and the developing fetus. These adjustments begin almost immediately and require the heart and circulatory system to adapt to a much larger workload than usual. The noticeable increase in heart rate is one manifestation of the body’s ability to meet the increasing metabolic demands of pregnancy. This change is expected and happens gradually, though it can sometimes feel alarming.
Understanding Cardiovascular Changes in Pregnancy
The primary reason for the accelerated heart rate is the dramatic increase in the volume of blood circulating throughout the body. By the end of pregnancy, a woman’s total blood volume can increase by up to 50% compared to her non-pregnant state. This additional fluid is needed to fill the maternal side of the placenta and to protect the mother from blood loss during delivery.
To move this much larger volume of blood, the heart must pump more efficiently, leading to a significant increase in cardiac output, the total amount of blood pumped per minute. Cardiac output typically rises by 30% to 50% during gestation. This increase is achieved through a combination of the heart beating faster and a greater volume of blood being ejected with each beat, known as stroke volume.
Hormonal shifts also play a direct role, with hormones like progesterone causing peripheral vasodilation, which means the blood vessels widen. This widening lowers the resistance to blood flow, and the heart compensates for this drop in resistance by increasing its rate to maintain adequate circulation. Furthermore, the heart muscle itself undergoes temporary changes, a process called cardiac remodeling, where the left ventricle expands to accommodate the higher volume.
Quantifying the Normal Heart Rate Increase
The expected increase in resting heart rate (RHR) is typically about 10 to 20 beats per minute (BPM) above the pre-pregnancy baseline. This represents a 20% to 25% elevation of the resting rate. For a woman whose RHR was 70 BPM before pregnancy, a rate around 80 to 90 BPM is expected and entirely normal.
This rise does not happen all at once but begins early, often starting around the eighth week of gestation. The heart rate continues to climb steadily throughout the trimesters, reaching its peak elevation sometime in the late second or early third trimester, often around 32 to 34 weeks. A resting heart rate up to 100 BPM is generally considered to be within the normal physiological range for a pregnant woman. The heart rate returns to its non-pregnant baseline within a few weeks to months after delivery.
Identifying Warning Signs and Symptoms
While a faster heart rate is normal, certain symptoms paired with it can indicate a need for medical evaluation. It is important to distinguish between common palpitations, which are brief and harmless, and symptoms that signal a potential medical concern. Any persistent or severe change in heart rhythm should be discussed with a healthcare provider to rule out underlying issues.
Symptoms that warrant prompt medical attention include chest pain, especially if it feels like tightness or pressure, or pain that radiates to the back, neck, or arm. Severe or sustained shortness of breath, particularly if it occurs while resting and not just during exertion, is also a concern. Episodes of fainting, severe dizziness, or lightheadedness should prompt an immediate call to a doctor.
A heart rate that remains persistently above 120 BPM, or palpitations that last for several minutes, should be quickly investigated. In some cases, a faster heart rate can be a sign of underlying conditions unmasked or exacerbated by pregnancy, such as severe anemia, hyperthyroidism, or preeclampsia. These conditions require diagnosis and specific treatment to ensure the health of both the mother and the baby.
Practical Steps for Managing Palpitations
For the common, non-threatening sensation of a racing heart or fluttering, there are simple lifestyle adjustments that can help manage the discomfort. Dehydration is a very common trigger for heart palpitations, so maintaining excellent hydration is highly beneficial. Drinking plenty of water throughout the day helps support the increased blood volume and overall cardiovascular function.
Avoiding certain triggers can also reduce the frequency of palpitations. Limiting the intake of caffeine and excessive sugar, both of which can stimulate the heart, is a practical step. Stress and anxiety are known to influence heart rhythm, so incorporating relaxation techniques such as deep breathing exercises, meditation, or prenatal yoga can be helpful.
Positional changes are another effective strategy, especially in later pregnancy. The weight of the uterus can sometimes press on major blood vessels when lying flat on the back, which can affect blood flow and trigger palpitations. Lying on the side, particularly the left side, can help improve circulation and alleviate these symptoms. Finally, prioritizing adequate rest allows the heart to work less strenuously, supporting the cardiovascular system through its increased workload.