Fetal Heartbeat in Pregnancy – Norms by Week and Detection Methods

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How the fetal heart is formed – the first contraction

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During the next week, a bend forms in the tube, where the first contraction occurs, which will then be heard as the baby’s heartbeat in the womb. Special cells are responsible for forming the bends, which, by attaching to the cells of the primary tube, “drag” them to the required area. Researchers have found that this process depends on a chain of chemical reactions, and the tension of the tube tissue also plays an important role in the formation of the heart. The bends may not form if it is not large enough.

What happens next

Over time, the future baby’s heart becomes increasingly similar to that of an adult. By the sixth week, the interventricular septum forms and begins to grow, followed immediately by the interatrial septum. The fetal heart acquires an almost adult appearance by the eighth week of pregnancy. 

It cannot be said that it is completely identical to an adult’s because oxygenated blood flows to the baby not from the lungs, but from the mother – at this time, the baby is not yet breathing independently, although the baby’s heartbeat is already clearly distinguishable. At this stage, all ventricles and atria function as a single hollow organ, and blood flows from one atrium to another through an oval open window. This is what a special opening in the interatrial septum looks like. When the newborn takes their first independent breath, it will close immediately after birth.

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The baby’s heartbeat during pregnancy at 6 weeks beats at a rate of 60 beats per minute. By this time, it consists of four hollow chambers with separate inlets and outlets for blood flow. In two weeks, the baby’s heart rate sharply increases and can reach up to 150 beats in 60 seconds. This is considered normal, even though it is twice as fast as the mother’s. The baby’s heart rate is very high during pregnancy at 9–10 weeks – the little human’s heart beats at a rate of 170 beats per minute. 

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In early pregnancy, the baby’s heartbeat is practically the only indicator that the pregnancy is progressing according to the established algorithm without deviations and anomalies. Therefore, the sooner a woman registers for pregnancy, the sooner the gynecologist can correlate the existing norms concerning the baby’s heartbeat by weeks with the real situation of the specific woman. This will allow serious congenital defects to be diagnosed at early stages, adjust the pregnant woman’s lifestyle and habits, and if necessary, prescribe necessary treatment. It is established that at the start of the 5th week, the heart rate is 80-85 beats per minute. Subsequently, the correspondence is as follows:

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8	{{{TEMP_MARK_{{{TEMP_MARK_82}}}8}}}
9	{{{TEMP_MARK_{{{TEMP_MARK_82}}}9}}}
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Second to third trimester, before birth	{{{TEMP_MARK_{{{TEMP_MARK_83}}}4}}}

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Causes of Heart Rhythm Disturbance

In each case of a child’s heartbeat irregularity, there are several causes. In the case of bradycardia, these may include:

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• multiple pregnancy.
• bad habits, vitamin deficiency, lack of fresh air;
• sedentary lifestyle;
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• infectious diseases;
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• premature placental abruption.

The causes that provoke tachycardia in a child’s heartbeat include:

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• Dehydration caused by prolonged toxicosis;
• Endocrine system diseases;
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• Intake of certain medications;
• Maternal heart and vascular diseases;
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There are also congenital heart pathologies in the child that are diagnosed with accompanying developmental delays.

Congenital Heart Pathologies 

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Echocardiography, including for pregnant women in the ‘risk group’, for whom there is an increased likelihood of heart defect development in the fetus for various reasons:

• If a defect is suspected during fetal ultrasound;
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• suffering from diabetes;
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• who have already had children with congenital heart defects.

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Ultrasound examination is performed from the first to the fifth month of pregnancy. In the early stages, the examination is conducted transvaginally – through the vagina, and later on through the abdominal wall – transabdominally. Throughout pregnancy, it is customary to have 3 ultrasounds. In the very first ultrasound, heartbeats are determined, in the second, heart chambers are inspected to rule out defects or other pathologies, and in the third, you can find out the baby’s gender.

CTG (cardiotocography) and auscultation

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Ways to Hear the Fetal Heartbeat on Your Own

To hear the tiny heartbeat, it is not necessary to wait for the next doctor’s visit. There are ways to listen to the baby’s heartbeat on your own, such as using a stethoscope. The device is inexpensive, but you will need an assistant to listen. Also, it will be difficult to hear the heartbeat before the 25th week. It is important not to confuse the heartbeat with the baby’s movement or the mother’s peristalsis. A fetal doppler is also used – a fairly expensive portable device with headphones allowing you to hear the baby’s heartbeat as early as the 8th-12th week. It is advisable not to use it often or for sessions longer than 10 minutes. It is possible to listen to the heartbeat by placing your ear close. Starting from the 30th week, the baby’s heartbeats become pronounced. They can be recognized simply by listening to the expectant mother’s belly.