Pregnancy affects a women's body in many ways, and one of these changes is your pulse rate, or the number of times your heart beats per minute. Also referred to as the heart rate, this increase in pulse reflects the heart working harder, pumping extra blood throughout the body. As part of routine prenatal care, and during labor and delivery, your doctor will monitor your pulse and other vital signs, such as blood pressure, in order to ensure they fall within safe ranges.
Heart and Blood Flow Changes
As the fetus grows, the uterus requires more blood flow in order to supply necessary nutrients for growth and development. As a result, the blood pumped by the heart increases by 30 to 50 percent, according to the Merck Manual. The heart rate at rest, which in nonpregnant adults usually ranges between 60 to 100 beats per minute, increases by 10 to 20 points during pregnancy, according to a September 2014 review published in "Circulation." According to this review, by the third trimester, the overall change in heart rate increases by 20 to 25 percent from baseline, or from the woman's heart rate before pregnancy.
Exercise Heart Rate
Heart rate increases when exercising, as the active body needs the heart to pump more oxygen-rich blood throughout the body. So when a pregnant woman exercises, her heart rate increases too. Instead of a specific heart rate guideline for exercise, the American College of Obstetricians and Gynecologists encourages women to choose moderate intensity exercises, which means there's enough movement to increase heart rate and cause some sweating. However, the intensity should be moderate enough that a woman can still talk while exercising.
Other Factors That Affect Heart Rate
Other situations or conditions influence a person's heart rate, and these factors can affect pregnant women too. According to the American Heart Association, heart rate can be increased in hot, humid weather, or when a person is stressed, anxious or dehydrated. Certain medications, such as beta blockers used for blood pressure, can slow heart rate. During labor, heart rate also increases as the amount of blood pumped by the heart increases by as much as 30 percent, according to the Merck Manual. If heart rate becomes too fast or irregular, treatment is needed to keep mom and baby safe.
Let your doctor know if you feel an abnormally fast heart rate, or if you have symptoms of dizziness, weakness or any episodes of fainting. While most women can continue their usual level of physical activity after getting pregnant, always consult your doctor before beginning any new or more strenuous exercise program. Your doctor may place limits on your activity or exertion level depending on your health and the health of your baby.
Reviewed by Kay Peck, MPH RD
- Merck Manual: Physical Changes During Pregnancy
- American Family Physician: Update On Prenatal Care
- Ultrasound in Obstetrics and Gynecology: Longitudinal Study of Vascular Structure and Function During Normal Pregnancy
- Circulation: Cardiovascular Physiology of Pregnancy
- The American Congress of Obstetricians and Gynecologists: Exercise During Pregnancy