Fetal heart rate: the norm for weeks, methods of control. When does the fetus's heart begin to beat?

2024 Author: Priscilla Miln | [email protected]. Last modified: 2023-12-16 00:21

For any pregnant woman, there is nothing sweeter than hearing a fetal heartbeat. And what could be better than a sound symbolizing the birth of a new life in the female body?! But here, what is interesting, at what time can one feel this marvelous music of a small heart? Let's try to figure this out. Tellingly, the sex of an unborn child can be determined from the heart rate (HR). But let's not get ahead of ourselves, let's consider everything in order.

First cherished sounds

Ko 2 or 3 weeks of development of the fetus in the womb, his heart begins to form. But so far it is a simple tube. For this reason, the expectant mother may not even know that she is already carrying a new life under her heart, which is at an early stage of development.

After two more weeksthe tube acquires an S-shape, because of this, this stage in the development of a child's heart is referred to as sigmoid. After another 4-5 weeks, a partition is formed inside the organ, as a result of which three chambers are formed. Someone may immediately have a question: "And when does the heart of the fetus begin to beat?". Just like that, starting from this moment, the little heart begins to make its first contractions.

During the first trimester, the general condition of the fetus is assessed by the heartbeat. During listening, three main characteristics are identified:

• HR.
• Rhythm.
• Beating pattern.

Only you can hear these sounds only with the help of the transabdominal method through special sensors. But if there are no special indications for this, then it is better to abandon this manipulation. And by the end of the 5th month of pregnancy, the baby's heartbeat can be heard through a regular medical stethoscope.

The need for listening

A baby's heart is tapped for a reason, and for good reason. And first of all it concerns the establishment of the fact of pregnancy. As soon as a woman has a delay in the menstrual cycle, the first thing she thinks about is that it is necessary to do an appropriate test. And with a positive result, many ladies go to the hospital in order to perform their first ultrasound.

When the heart of the fetus begins to beat, we have already found out, now it is worth understanding why exactly you need to listen to it. But it is not always possible to detect a heartbeat, which is not yet a pathology. It is mandatorywill make itself felt, but a little later. It is worth worrying in those cases when, during the re-examination, nothing is still heard. This may indicate that the fetal egg is deformed, which is not good. Often, in this case, a missed pregnancy is diagnosed, in which an abortion should be performed due to medical reasons.

In addition, the heartbeat allows you to assess the state of the fetus in the womb. At the same time, the body is able to feel everything that happens in its environment. When an expectant mother experiences stress, she has some kind of ailment, or she exposes herself to excessive physical exertion, the oxygen saturation of the fetus drops. As a result, this is reflected in the form of deviations from the norm of the fetal heartbeat. But, as a rule, such changes are temporary, and the rapid work of a small heart is usually due to impaired blood supply to the fetus, which is referred to as fetoplacental insufficiency. Often this condition becomes chronic, and therefore does not lead to compensatory changes.

In addition, the heartbeat allows you to assess the condition of the child before childbirth. During this process, he and his heart are exposed to enormous loads: compression, a small amount of oxygen. At the physiological level, the child's cardiovascular system has already prepared, acquiring stress resistance for the entire period of pregnancy.

However, sometimes the umbilical cord can be clamped, or in the case of placental abruption, there isserious danger. There may also be other equally threatening conditions. For this reason, obstetricians vigilantly monitor the baby's heartbeat after each contraction.

Ways to listen to the heart

Before we touch on the fetal heart rate, let's look at exactly how you can listen to it. Usually, various devices are used for this. Moreover, depending on the gestational age, this or that diagnostic method is used:

• Ultrasound.
• Echocardiography (ECG).
• Auscultation.
• Cardiotocography (CTG).

Ultrasound

Ultrasound is the very first method that is used to assess the condition of the fetus. Moreover, starting from the first month of pregnancy. At earlier dates, a transvaginal (vaginal) examination is performed, and at a later period, a transabdominal method (through the abdomen) is used.

This method allows you to identify all sorts of pathologies, and at an early stage of pregnancy. For the entire time of bearing a child, a woman must undergo an examination at least three times.

Already on the first visit, the first fetal heartbeat can be detected. During the second visit, you can view his cameras, which will reveal the presence of defects or other deviations. If the doctor has some suspicions, then he prescribes an additional study, during which all 4 cameras will be “visible”. As a result, up to 75% of probable pathological conditions of the child's heart are detected by doctors.

During the 2nd and 3rd trimestersWith the help of ultrasound, the volume of the organ and its position are determined. Under normal conditions, the heart is located in the region of a third of the volume of the chest.

Echocardiography, or ECG

As a rule, this study is prescribed for pregnant women in the case when several violations were detected during the ultrasound:

• delayed fetal development in the womb;
• deviations in the work of the heart;
• pathological condition of the fetus;
• anomalies in the structure of the heart.

ECG allows you to evaluate not only the fetal heartbeat, but also the structure of the main organ of the circulatory system, and in detail: whether it performs all the functions, and whether there are blood flow disturbances in all its chambers. For this, one- and two-dimensional images, dopplerometry, are used. To obtain a reliable result, it is better to conduct such a study from 18 to 28 weeks according to the obstetric gestational age.

In addition, a woman can be prescribed an ECG when she reaches the age of 38, in the presence of any endocrine disease (diabetes mellitus), cardiovascular disease (CHD or congenital heart disease). In addition, if the expectant mother suffered an infectious disease during pregnancy, or gave birth to children with CHD, the gynecologist may also prescribe her an echocardiogram.

Auscultation

This technique is applicable from the onset of 5 months of pregnancy. Its essence lies in listening to heart rhythms with a stethoscope through the surface of the abdomen. The procedure is carried out not only at every visit by a woman to a gynecologist. Immediately during childbirth, every 20 minutes, the obstetrician listens to the fetal heartbeat in order to assess the condition of the child.

In addition, the doctor can determine its position in the womb:

• Head presentation - in this case, the heartbeat can be heard below the navel.
• The transverse position of the fetus is indicated by listening to heart rhythms at the level of the navel.
• Breech presentation is detected by listening to heartbeats above the navel.

In addition, during auscultation, you can determine the rhythm and nature of the heartbeat. Which, in turn, implies the possibility of detecting not only hypoxia, but also developmental pathologies.

At the same time, such a procedure may become ineffective in some cases:

• When the placenta is located on the anterior wall of the uterus.
• With a large amount of amniotic fluid or, conversely, oligohydramnios.
• Multiple pregnancy.
• The woman is obese.

But despite this, auscultation is considered a fairly reliable and easy-to-use method for measuring the fetal heartbeat.

Cardiotocography, or CTG

This technique is based on the registration and collection of analyzes of the work of the heart muscle under different conditions, in motion or not, during uterine contractions, against the background of exposure to various kinds of stimuli. In the presence of oxygen deficiency, the method is able to detect such a condition without problems.

Danger of hypoxia, whichis oxygen deficiency, is to reduce the adaptive capabilities of a very young organism, which often results in a slowdown in its development and growth. As a result, there is a high risk of various pathologies during childbirth and after.

Through CTG, two parameters of the fetal heart rate are determined:

• heart rate variability;
• basal rhythm.

The term "basal rhythm" refers to the heart rate during the movement of the child and in its absence. Normal heart rates are 109-159 beats per minute at rest and 190 when moving.

As for the rhythm variability, this is the difference in heart rate between the state of rest and when moving. With normal development, the parameter should be from 5 to 25 contractions, no less and no more. Any deviations from the norm are considered pathological. At the same time, based only on these values, such conclusions should not be drawn, since additional studies are needed.

Varieties of CTG

When prescribing cardiotocography, it can be done in one of two ways:

• External (indirect) examination.
• Internal (direct) research.

In indirect diagnosis, the fetal heartbeat and uterine contractions are examined using special sensors placed on the abdomen. This method has no contraindications and can be used not only during pregnancy, but also during direct childbirth.

WhatAs for direct diagnosis, it is used in the rarest cases and only during the birth of a child. The study is conducted using several devices: an ECG electrode, which is attached to the child's head, and a sensor inserted into the uterus.

The result is evaluated according to a special point system. 9-12 is considered normal. 6-8 points indicates mild hypoxia, as a result of which the next day the woman will have to undergo a second examination. 5 - this is already a pronounced oxygen starvation, which poses a serious threat to the baby (or baby). In this case, you have to give birth only by caesarean section.

Weekly heart rate readings

Typically, the fetal heartbeat is uneven throughout the weeks of pregnancy, and gradually accelerates each time. Initially, the work of the heart is similar to the maternal rhythm. But subsequently, the heart rate begins to increase, which is due to the accelerated formation of the body of the crumbs. The highest frequency of muscle contractions occurs at 9-10 weeks of pregnancy, but then it drops.

By the arrival of 14-15 weeks, the main organs and their systems have already been formed, in the future they only grow. By the last date, the heart rate can vary from 130 to 160 beats per minute. For greater clarity, below is a figure that shows the normal indicators of the fetal heart rate by week.

With the onset of 12 weeks of gestation, the heart rate can determine its gender:

• Less than 140 beats per minute - a boy.
• More than 140 beats perminute - a girl will appear.

Thus, you can see that in girls the heart works much more intensively than in boys. At the same time, the heart rate is also different: again, in the male half it is measured, while in the female it is more chaotic.

Possible deviations

We have already familiarized ourselves with the normal performance of a child's heart from the table above. But in some cases there can be serious deviations. So, changes in heart rate may indicate such conditions:

• Tachycardia. This condition can be caused by insufficient blood circulation of the uterus and placenta, a small amount of hemoglobin in the mother's circulatory system, fetal anemia, placental insufficiency, placental abruption. Also, fetal heart palpitations can be observed due to a pathological condition of the heart, a high temperature of the expectant mother, an inflammatory process of the membranes, taking drugs like atropine or ginipral, an increased level of intracranial pressure and a number of other factors.
• Bradycardia. The development of this condition is facilitated by the long position of the expectant mother on her back. This causes compression of the inferior vena cava. but there may be other reasons besides this: treatment with propranolol, heart defects.

All of the above should not be underestimated due to the gravity of the situation. For such reasons, a woman needs proper treatment, and in some cases, a caesarean section cannot be dispensed with.

In closing

In the end, it remains to wish eachexpectant mother to monitor their condition, especially during pregnancy. It is necessary to strictly follow all the recommendations of the doctor who leads the entire process. In particular, this applies to ultrasound and other necessary and additional procedures.

It is no coincidence that during each scheduled ultrasound, the doctor listens to the baby's heartbeat. His heart rate, rhythm and nature of heart contractions can tell a lot about a specialist. Sometimes you can even determine the sex by the heartbeat of the fetus. It is clearly not worth ignoring such examinations if a woman wants to hug her full-fledged and, most importantly, he althy child!