It is a common experience during pregnancy to feel a rhythmic sensation in the abdomen, leading many to wonder if they are feeling their baby’s heartbeat. The clear answer is that what you are feeling is not the fetal heart. This sensation is actually your own pulse, which is made more noticeable due to the physical changes occurring in your body during pregnancy. This article will explain the physiological source of this abdominal pulse, detail why the fetal heartbeat cannot be felt externally, and describe how healthcare providers monitor the baby’s heart rate.
What Causes the Pulsation in Your Abdomen
The rhythmic thumping a pregnant person feels is primarily the pulse of the maternal abdominal aorta, the body’s largest artery, which runs down the back of the abdominal cavity. Pregnancy significantly increases the volume of blood circulating through the body, often by 35% to 45%. This substantial increase means a larger volume of blood is pushed through the aorta with each beat, amplifying the pulse.
As the uterus expands to accommodate the growing fetus, it takes up more space within the abdomen. This expanding organ can press against the abdominal aorta, especially when the mother is lying flat on her back. This compression brings the artery closer to the abdominal surface, making its strong pulse more perceptible through the skin and surrounding tissues.
This palpable rhythm matches the mother’s own heart rate exactly. The mother’s pulse is usually between 60 and 100 beats per minute, whereas a normal fetal heart rate is much faster, ranging from 110 to 160 beats per minute. This pulsation is a normal physiological phenomenon of pregnancy, often becoming most apparent in the second or third trimester.
Why You Cannot Feel the Fetal Heartbeat
The fetal heart cannot be felt externally by touch due to several layers of physiological cushioning and the small size of the heart itself. The fetus is suspended in amniotic fluid inside the uterine wall, which acts as a dense protective and acoustic buffer. These layers of fluid, muscle, and tissue effectively dampen any tiny vibrations produced by the rapidly beating fetal heart.
The fetus is positioned deep within the mother’s body, protected by abdominal fat and muscle tissue. The fetal heart, particularly in early pregnancy, is simply too small and its sound too faint to transmit a palpable pulse through all these layers to the outside skin. The mechanical action required to generate a pulse strong enough to be felt externally is simply not possible for the developing organ, which is why medical professionals rely on specialized equipment to detect the heartbeat.
How and When Doctors Monitor the Fetal Heartbeat
Healthcare providers use specific medical instruments to successfully detect and monitor the fetal heartbeat, as external detection is not possible. The most common tool is the Doppler ultrasound, a handheld device that uses sound waves to amplify the fetal heart tones. This device is typically used during routine prenatal visits starting late in the first trimester.
The fetal heart begins beating around five to six weeks of gestation, and a heartbeat can often be seen via a transvaginal ultrasound at this early stage. The heart sounds usually become strong enough to be detected by the external Doppler device around 10 to 12 weeks of pregnancy. It may take slightly longer to hear the heartbeat depending on factors like the position of the fetus or the placenta.
When to Contact a Healthcare Provider
In rare instances, a strong, persistent, and painful pulsing sensation in the abdomen may warrant contacting a healthcare provider. While the feeling is almost always benign, a pulsing mass can occasionally be a symptom of a much rarer maternal health issue, such as an abdominal aortic aneurysm. Seeking medical advice is appropriate if the pulse is accompanied by severe pain, dizziness, or a rapid heart rate.