Fertilized egg 12 mm embryo. How is the size of the fertilized egg calculated? Implantation of the fertilized egg - signs, symptoms and characteristics. What does a fertilized egg look like?

Early ultrasound during the initial stages of pregnancy has many advantages. It does not harm the health of the expectant mother and child and provides a lot of information for the doctor.

Size ovum during pregnancy - one of the most important indicators, especially during the beginning of pregnancy.

fertilized egg

Before moving on to the parameters of the baby and amniotic organs, it is worth understanding what a fertilized egg is?

The formation of this new living organism begins from the moment the egg is fertilized by the sperm. This occurs inside a woman's fallopian tube. Next, the fertilized cell passes into the uterine cavity and begins to divide into small cells.

Several cells that have approached the wall of the womb and begun implantation can already be called a fertilized egg. There is nothing in it yet similar to the human body, but very soon this will change.

A week after fertilization, the cells are implanted into the wall of the uterus, after which they begin to exist at the expense of the mother’s body. At this time, the embryo is still very small and cannot be seen on an ultrasound.

After implantation, thanks to substances from the uterine wall that enter through the blood vessels, the new organism begins to grow rapidly. It can be determined by instrumental methods in just a few weeks.

How is it determined?

You can see the size of the baby using a simple transabdominal ultrasound. The study is performed as follows:

• After a woman is registered for pregnancy, the doctor determines the date of the first screening - usually 11-14 weeks.
• The woman lies down on the couch, after which the procedure begins.
• An ultrasound sensor is placed on the expectant mother’s belly and all dimensions of the fetus are carefully assessed.
• This study can be performed earlier, but it will be less informative.

At what size of fertilized egg is the embryo visible? Already at 3–4 weeks of gestation, modern sensors are able to assess the presence of a baby in the uterine cavity, at which time it reaches a size of about 3 mm.

An embryo of 5 mm is already clearly visible on ultrasound, but assessing its internal structure is still quite difficult.

Norm

Most often, women are interested in the size of the embryo even before the time of the first screening. This is necessary to know in order to determine the fact of pregnancy, its duration and detect developmental abnormalities.

During the procedure, the doctor evaluates the shape of all detected formations and the parameters of the internal contents of the fertilized egg.

Size of fertilized egg by week of pregnancy, table:

As can be seen from the table, the size of the fertilized egg increases quite quickly. It is assessed only in the first trimester of pregnancy. Next, the doctor will determine more accurate parameters that reflect the state of the child’s body.

Pathology

When performing an ultrasound examination in the early stages of pregnancy, a fairly large number of different abnormalities can be detected. Among them are the following groups of disorders:

1. Change in the shape of the primordium. At the beginning of pregnancy, the embryo is a spherical formation, so on ultrasound it is detected in the form of a circle. After 7 weeks of pregnancy, the fetus takes on an oval shape. Tumors of the uterus, congenital malformations, infectious diseases, pathology of the placenta can cause disruption of the shape of the egg.
2. Pathology of location. A properly developing embryo is located in the uterine cavity in the area of ​​the fundus or posterior wall of the organ. Less commonly, the embryo is located in the area of ​​the internal os. Other options for the location of the baby are considered pathological, some of them are generally incompatible with the further physiological course of pregnancy.


3. Anembryony. A rather rare developmental defect in which there is no embryo at all in the fertilized egg. Due to genetic disorders and the influence of factors external environment The amniotic organs develop, but the baby itself does not. In this case, the egg will be of normal size, but there will be no child inside it.
4. Dimensional changes are the most common deviation. In the first stage of pregnancy, it is quite difficult to draw a conclusion about the normal size of the embryo, but often already at this time it is possible to guess what is causing the decrease or increase in the fetus.

Pathology of sizes

What could be causing the change in the size of the fertilized egg? Let's try to understand this issue.

If the baby's size is less than the normal gestational age, you should think about the following reasons:

• The gestational age was incorrectly determined. Early ultrasound can estimate gestational age using fetal size. If there are no unfavorable factors for the development of pregnancy, it is worth thinking that clinically the gestational age was established incorrectly.
• Infectious diseases - viral and bacterial factors in the early stages of gestation can seriously affect the development of the embryo. In this case, the fertilized egg may slow down its growth or not grow at all.


• Genetic disorders - in response to the presence of genetic abnormalities in the fetus, the female body may stop developing pregnancy, which will subsequently lead to miscarriage.
• Exposure to environmental factors - chronic stress, lack of sleep, poor diet, bad habits. All these factors can slow down the growth and development of the baby, while the fertilized egg will be less than term.

It is much less common to detect fetal enlargement in comparison with the age norm. This may also indicate an incorrect timing of conception. In other cases, an increase in size may be a manifestation of congenital aberrations in the development of the skeleton and central nervous system, infectious lesions of the fetus, as well as endocrine diseases of the mother.

Further tactics

If during the examination a violation of the size of the embryo or other indicators of the fertilized egg is determined, you should not panic. This screening is only a preliminary examination.

Further actions of the doctor and mother:

1. Evaluate other parameters obtained during the survey.
2. Repeat ultrasound examination in a few weeks.
3. Eliminate exposure to adverse environmental factors, check for chronic infections.
4. If there are risk factors, start taking vitamin complexes and other medications.
5. Pass all the first screening tests and be examined by specialist doctors.
6. If indicated, perform invasive studies, such as amniocentesis.

Only after receiving all of the above results can more accurate conclusions be drawn and the question of the possibility of prolonging pregnancy can be decided.

The size of the fertilized egg is the very first size of your baby in the earliest stages of pregnancy. It is measured before it becomes possible to measure the height, weight, length of the baby’s limbs, and in the early stages it is the size of the fertilized egg that is very informative for establishing the gestational age from the date of conception, as well as for assessing the growth rate of the embryo.

How and why are measurements taken?

The fertilized egg completes its formation by the third week from the day of conception; it is by this time that it can already be seen on an ultrasound (this is about a week of missed periods). It consists of the embryo itself, membranes, chorion, amnion and yolk sac. The chorion is responsible for attaching the embryo to the wall of the uterus and nutrition, for the production of hormones necessary for the continuation of pregnancy. The amnion forms the aqueous environment (amniotic water), the yolk sac is a food supply, and inside the fertilized egg is your unborn child looks like a thin strip.

Detection of a fertilized egg in the uterine cavity against the background of a delay in menstruation - reliable sign pregnancy, but in the very early stages the doctor will not be able to clarify anything more.

The fact is that there can be two embryos in one egg (twins), and this will become noticeable much later. Sometimes the fertilized egg turns out to be empty, that is, there is no embryo in it, and in the early stages this is also not visible.

The size of the fertilized egg is determined to clarify the gestational age and to assess the correctness of early embryonic development.

How do sizes change? Until the 8th week of pregnancy, doctors have almost no opportunity to understand how the baby itself actually grows and develops, because its size is very small. Measuring individual parts of the body is technically impossible, and this is where the size of the fertilized egg comes to the rescue. It grows according to certain obstetric terms

, and for different children at the beginning of pregnancy this indicator is very similar. It is later that children become large and miniature, with large heads or small hands, in a word, the way nature intended them. And during the period of embryogenesis, while organs and tissues are actively forming, growth rates are approximately the same for everyone. That is why the size of the fertilized egg and the dynamics of its growth - important indicators

to confirm the deadline.

When talking about the size of the fertilized egg, they mean one size - it is called SVD (average internal diameter). It is a segment laid by a somnologist between the walls of the egg so that its ends are on opposite sides.

Values ​​such as the volume of the gestational sac and its area do not play a large diagnostic role, but are often also measured simply because their determination is provided for by the program of a particular ultrasound scanner.

Therefore, we present a summary table of norms.

Table of standard values ​​of SVD, KTR and other indicators

Do not panic or worry if the size of the ovum according to the results of your ultrasound differs slightly from the norm. Individual fluctuations downward are quite possible if ovulation was late, implantation took place later than 7–8 days after ovulation, and large sizes may indicate that ovulation occurred earlier or early implantation took place.

Reasons for deviations

A long-awaited pregnancy is a condition in which women are very suspicious; they can be upset and alarmed by anything. Especially - incomprehensible and complex terms that a doctor can use when determining the size of the ovum. For example, the concept of “deformed” can be confusing. There's nothing to worry about - in 90% of cases the egg is deformed due to increased tone of the uterine muscles.

If you remove the tone, the outline of the egg will become correct. In other words, deformation is not a pathology. Possible problems include the following:

Hypoplasia

The embryo grows faster than the shell. At the same time, it is observed discrepancy between SVD and CTR - the coccygeal-parietal size exceeds the norm in terms of time, and SVD is below the norm. This may be a consequence infections, hormonal disorders, embryonic malformations. Very often the cause remains unknown.

The prognosis is unfavorable; embryo death occurs in the vast majority of cases. A frozen pregnancy develops. The second option is spontaneous miscarriage until the death of the embryo. There is no positive outcome and further continuation of pregnancy with hypoplasia of the ovum.

Hydatidiform mole

There is no embryo. There are only overgrown chorion membranes, forming multiple blisters-cysts. They look like grapes and can be accurately diagnosed using ultrasound. The reason is a low-quality egg, which, when merging with a male reproductive cell, could not provide a complete set of DNA for this process. Dad's chromosomes simply double, and such an embryo, even if it is partially present, cannot grow and develop.

The hCG level is usually significantly higher than normal, a woman may think that she is carrying twins or triplets.

In every fifth woman, a hydatidiform mole develops into a malignant formation, prone to rapid and aggressive metastasis - chorionepithelioma. Therefore, it is important to remove the skid as early as possible - as soon as it is discovered.

Anembryony

The fertilized egg is present and growing, but there is no embryo. This can be detected only after 6–7 weeks, when it is time to record the heartbeat and CTE. There is none of them. The cause usually lies in a genetic error, acute infection, exposure to radiation and other factors, not all of which have been studied.

It is important to conduct the examination over time. If after a few days or a week the embryo is not detected, curettage of the uterine cavity or vacuum aspiration is indicated.

Egg too large

A significant increase in the size of the fertilized egg sometimes indicates pathologies of the fetus and pregnancy. Often, with a large egg, a decrease in CTE and a disturbance in the fetal heart rhythm are detected. In this case, the doctor may suspect that such signs are harbingers of fetal development stoppage.

If excess size is detected in the early stages (for example, at 6 weeks), a blood test for hCG is prescribed. It is possible that two monochorionic twins develop inside one egg. And if the blood results confirm this, then after a few weeks a repeat ultrasound is needed to measure each of their embryos.

You should not draw conclusions based on the tables and standards indicated as indicative. If now the egg size is lower or higher than normal, this does not mean that in a week or two the deviation will persist. Sometimes it is enough to calm down, stop worrying, take a weekend and lie down at home with a book, drinking warm tea and No-Shpu, so that the muscles of the uterus relax, the deformation is eliminated, and the size becomes normal.

If a gross anomaly is discovered (anembryonia, hydatidiform mole, etc.), you should not give up. It didn’t work out with the birth of the baby this time - it will work out next time, because these anomalies do not affect the subsequent ability to get pregnant, carry and give birth to a fully-fledged child.

The main thing is now, at this stage, to use all medical capabilities to find out the reasons, to visit a geneticist before planning the next conception.

After a positive pregnancy test result, a woman short terms should contact antenatal clinic, where for nine months she will be under the supervision of a doctor, periodically undergo laboratory tests, and undergo examinations that will help monitor the development of the fetus and the woman’s health.

One of the necessary, reliable and informative diagnostic methods is an ultrasound examination, which allows you to confirm the presence of pregnancy, monitor its progress, also if complications or fetal anomalies are suspected, promptly eliminate the cause or take measures to preserve the woman’s health.

A routine ultrasound examination during pregnancy should be carried out three times (10 - 13; 16 - 21; 32 - 36 weeks) but, sometimes, at the request of the woman, or on the direction of the doctor, it is carried out no earlier than 3 - 6 weeks after conception, when The egg is firmly attached to the uterine cavity.

This period allows you to see the presence of a uterine or ectopic pregnancy, attachment of the fertilized egg, and others important elements, on which the development of the fetus and the health status of the woman depend.

After conception, the most accurate ultrasound method is considered (a sensor is inserted into the vagina) or transabdominal (performed through the anterior wall of the abdominal cavity) - during the examination, visualization of the fertilized egg in the uterine cavity or outside its cavity is determined, which indicates an ectopic pregnancy.

Sometimes ultrasound equipment does not detect the fetal membrane until 5, but an experienced doctor should notice changes in the layers of the uterus, where thickening and compaction of the uterine walls are visible, which is typical for pregnant women. In such cases, a repeat examination is scheduled after one or two weeks.

Implantation of the fertilized egg after conception:

fertilized egg- this is the membrane of the embryo, which in the first trimester of pregnancy contributes to the development of the unborn child, and should normally correspond to the size and diameter of the embryo.

After fertilization, the egg must be fixed in the uterine mucosa for 10 days, where human chorionic gonadotropin begins to be released, which allows the pregnancy test to show positive results, and the woman suspects the first signs of pregnancy. At this stage, an ultrasound examination will not be able to provide objective indicators, so this diagnosis can be carried out no earlier than the fourth week after conception, when the embryo develops in the fertilized egg.

Development of the fertilized egg

Using ultrasound, you can visualize the membrane of the embryo, its shape, size from 3 to 6 weeks. This depends on the characteristics of the woman’s body, the qualifications of the doctor and the quality of the equipment. To assess the size and growth of the ovum, the following indicators are used:

1. average internal diameter (SVD);
2. coccygeal-parietal size (CTP).

The results of this examination are recorded in the pregnant woman’s chart.

• Starting from 3 weeks after conception, the egg has an oval shape, in the normal course of pregnancy, the size of which is SVD 15 mm, and thickening of the walls of the uterus is noted, which allows the doctor to confirm conception.
• At 5 weeks, the membrane increases significantly in volume, takes on an elongated shape, and occupies the entire uterine cavity. SVD at this stage is from 18 mm. During this period, the embryo's cardiovascular system begins to develop.
• With an ultrasound examination at 6 weeks, the egg has a spherical shape, and the SVD is 21 -23 mm, and at this period it is also possible to determine the CTE of 6 mm and the heart rate.
• At 7 weeks it takes on an oval-elongated shape. SVD 23 - 24 mm, KTR 10 -11 mm. During this period, the doctor can clearly see the movement of the fetus and determine the attachment of the placenta.
• Starting from 8 weeks, the embryo has an oval-elongated shape, SVD is 29-30 mm, CTE is 16 mm and occupies most of the uterus, and the structure of the embryo is clearly visible on ultrasound.
• At 9 weeks, the oval-elongated shape remains. SVD reaches 33 mm, CTR 23 – 31 mm. During this period, ultrasound indicates the placenta insertion, the activity of the embryo is also visible, and the shape of the head and torso of the fetus is measured.
• At 10-11 weeks, the fetus occupies the entire uterine cavity. SVD has 39 – 41 mm, KTR 31 – 41 mm. During this period, the echo-positive membrane disappears, the fetus begins to develop in the placenta, which is clearly visible on ultrasound.
• From 12 to 13 weeks the fetus is clearly visualized; the biparietal dimensions of the head, torso, and internal organs can be measured. SVD reaches 56 mm, KTR 53 mm. During this period, you can see the exact duration of pregnancy and other important indicators of the first trimester.

In the very early stages of pregnancy, some indicators may deviate from the norm or be difficult to diagnose using ultrasound; this depends on the quality of the equipment and the doctor’s experience.

Also, during a multiple pregnancy, identifying two fertilized eggs is much more difficult and is possible no earlier than on the 6th - 8th. If there are significant deviations from the norm, anomalies may develop. An ultrasound examination up to 9 weeks is carried out if the woman or the doctor is not sure about conception, or there is a history of diseases of the ovaries, uterus, or when early miscarriages were observed in the past.

Abnormalities of the ovum

There are several types of anomalies and pathological processes during the development of the fetal membrane. Many women are interested in the question: – Why, and for what reasons can anomalies be observed?

There are a huge number of reasons why the fertilized egg cannot develop correctly. These include chronic diseases of the mother, heredity, internal infections, improper attachment of the egg and other unfavorable factors. Anomalies include:

1. change in shape - can occur with partial placental abruption, or with a violation of the tone of the uterus. With timely diagnosis of deformation of the ovum and normalization of the tone of the uterus, it begins to take on the correct shape and does not threaten the life of the embryo and the woman;
2. disruption of the implantation process - improper attachment of the egg;
3. anomaly of location - attached to the lower part of the internal pharynx;
4. size violations - when the egg does not meet the required parameters;

Anomalies are quite common, but most of them are not a threat to a woman’s life if they are diagnosed in time. Also, the possibility of conceiving and giving birth to a healthy child in the future in case of a failed pregnancy is not excluded.

The following pathologies are considered more dangerous, which do not allow saving the fetus and can threaten the life of a woman:

• frozen pregnancy - the membrane of the unborn fetus stops growing and developing, and the embryo dies. With this pathology, the embryo is scraped out of the uterine cavity.
• trophoblastic disease of the embryo - characterized by the formation of a benign tumor inside the fetal egg. The cause of the development of pathology is often decidual endometritis or other gynecological diseases.
• anembryonia is a pathology that is characterized by the absence of an embryo in the fertilized egg, which increases in volume, can be filled with serous fluid, but does not contain an embryo inside. Such a pathology can only be detected using an ultrasound examination no sooner than in the seventh week after the expected conception.
• polyhydramnios - excessive accumulation of amniotic fluid in the amniotic cavity. This condition can lead to placental abruption and embryo death.
• oligohydramnios is much less common and is characterized by an insufficient amount of amniotic fluid in the amniotic cavity. This anomaly can be diagnosed as early as 9–11 weeks of pregnancy.

You should undergo ultrasound examinations from a highly qualified specialist, and you should also pay attention to the capabilities and quality of the equipment. You should not put much faith in the reliability of the examination 3–4 weeks after conception, since the equipment can often make mistakes.

Therefore, doctors recommend undergoing an ultrasound examination only when the embryo can be clearly seen (6 – 9 weeks). If abnormalities are suspected, the doctor will re-order an examination after one or two weeks.

Implantation of the fertilized egg - signs of this phenomenon appear early in pregnancy. Despite the fact that the expectant mother does not actually feel them, they are very important for the further development of the fetus, since without implantation the embryo simply will not develop.

When does implantation of the fertilized egg occur? Characteristic signs and features.

Implantation of the fertilized egg may have earlier symptoms, but these are indirect, meaning that they are not necessarily caused by conception, even if it did occur. These signs include scanty bloody discharge. However, it must be taken into account that such discharge can also be pathological in nature. It should be borne in mind that implantation bleeding cannot be profuse, it occurs very rarely, and in fact always goes unnoticed by expectant mothers. You can predict implantation of the fertilized egg by the presence of discharge approximately four to seven days after unprotected sex.

How does the fertilized egg change? Sizes by week throughout pregnancy.

Initially, the fertilized egg has an oval shape. Using ultrasound, the SVD of the fetal egg is determined by week. Since this value is variable, there is a certain error in determining the period based on this fetometric indicator. This error averages one and a half weeks. As a rule, the gestational age is determined by other parameters, for example, by the value of the fetal CTE (or coccygeal-parietal size) and so on.

If the diameter of the fertilized egg is 4 millimeters, then the gestation period is very short - up to six weeks. Most likely, no more than 4 weeks have passed since conception. Already in the fifth week, the SVD reaches 6 millimeters, and after three days the fertilized egg becomes 7 millimeters in diameter. In the sixth week it grows to 11 - 18 millimeters, while an SVD of 16 millimeters indicates six weeks and five days of gestation.

If you are interested in how quickly the fertilized egg grows, then we can say with confidence that until the 15th - 16th week of pregnancy, its size increases by one millimeter every day. After this, the size of the fertilized egg begins to increase by 2 - 2.5 millimeters daily. It should be taken into account that after the 16th week of pregnancy they usually stop measuring CTE and begin to focus on other indicators.

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The beginning of pregnancy is the most exciting time, especially when it is a long-awaited child. In the first weeks, a woman should lead a moderate lifestyle to allow the fertilized egg to gain a foothold in the uterus and begin to develop (strong physical exertion, overheating and serious illnesses during this period can provoke an involuntary miscarriage). Today we’ll talk about how the size of the fertilized egg changes over the weeks.

So, it is possible to see the unborn child for the first time during an ultrasound, which is usually prescribed at 10-11 weeks. However, many mothers are so impatient that they go to a specialist immediately after a delay (5-6 weeks) to confirm the fact of conception.

What is a fertilized sac?

The size of the ovum on the first ultrasound

The first photo will show an oval formation, since at such an early stage the embryo that will develop in the fertilized egg is not yet visualized. If the eggs are not visible, the specialist will prescribe a second ultrasound after a couple of days. If by the seventh week of the delay an oval does not appear on the monitor, most likely the woman will be informed that the pregnancy is not developing (in this case, additional cleaning may be required if a frozen pregnancy has occurred).

Is it possible to determine the gestational age by the size of the fertilized egg?

To get the most reliable result, they additionally look at the coccygeal-parietal size of the fetus (it is measured only until the 16th week, after which other indicators are used to clarify the gestational age).

Size of fertilized egg by week of pregnancy (table)

When conducting the very first ultrasound examination, which is done when menstruation is delayed and in order to accurately diagnose the presence of intrauterine pregnancy, the fertilized egg can be examined. It is when the doctor sees this miniature formation on the monitor that he already informs the woman that she will soon become a mother. On the monitor you can see the fertilized egg, which is a small oval-shaped formation. In the early stages, the embryo, which will subsequently develop and grow in the fertilized egg, is not yet visualized, but soon it will grow up, and then it will be possible to clearly see it.

An empty fertilized sac is an egg without an embryo when pregnancy does not develop. The embryo is often visible already from the fifth week of pregnancy, but sometimes there are cases when even at this stage the doctor does not see the embryo during an ultrasound examination, in such a situation a repeat ultrasound is prescribed. Very often, a repeat ultrasound shows both the embryo and its heartbeat. When the embryo is not visible after six to seven weeks, then, unfortunately, there is a high risk that the pregnancy will not develop. In this article we will look at the norms of the fertilized egg by week.

What is a fertilized egg

The fertilized egg consists of embryonic membranes and an embryo. This period of pregnancy is its first stage of development. And it all starts with the fusion of two cells – male and female.

Then the fertilized egg actively begins to divide, first into two parts, then into four, and so on. The number of cells, like the size of the fetus, is constantly growing. And the entire group of cells that continue the division process moves along the fallopian tube to the zone of its implantation. This group of cells is the fertilized egg.

Having reached its goal, the fertilized egg attaches to one of the walls of the woman’s uterus. This occurs a week after fertilization. Until this time, the fertilized egg receives nutrients from the egg itself.

• Fertilized egg 2 weeks after insertion into the uterine cavity, it nourishes the swollen mucous membrane of this reproductive organ, which is already prepared for the process of development and nutrition of the fetus until the time of formation of the placenta.
• The baby's place, or placenta, is created from the outer shell ovum at 3 weeks, which at this time is already densely covered with villi. These villi at the site of attachment of the fertilized egg destroy a small area of ​​the uterine mucosa, as well as the vascular walls. Then they fill it with blood and immerse it in the prepared area.
• In general, the fertilized egg is the very first sign of a normally ongoing pregnancy. It can be examined by ultrasound after two weeks of missed menstruation. Usually in this case it is visible fertilized egg 3-4 weeks. The embryo becomes noticeable only at 5 weeks of pregnancy. However, if the doctor diagnoses the absence of an embryo in fertilized egg 5 weeks- in other words, an empty fertilized egg, then the ultrasound is repeated again after a couple of weeks.
• Usually in this situation, at 6-7 weeks, the fetus and its heartbeat begin to be visualized. When fertilized egg at 7 weeks is still empty, this indicates a non-developing pregnancy. In addition to this complication, others may appear in the early stages of pregnancy - incorrect location of the fertilized egg, its irregular shape, detachments, and others.
• It is for this reason that it is important to undergo an ultrasound examination as early as possible, so that the situation can be changed if it can be corrected. Since in the first trimester ( fertilized egg up to 10 weeks) high probability spontaneous miscarriage, detachment and other pathologies. However, enough about the sad things.

Fertilized egg at 6 weeks and until this stage of pregnancy it has an oval shape. And an ultrasound examination usually evaluates its internal diameter - the SVD of the fetal egg. Because fertilized egg size 7 weeks or at another stage of pregnancy is a variable value, that is, the error in identifying the gestational age using this fetometric indicator.

On average, this error is 10 days. Gestational age is usually determined not only by this indicator, but also by the values ​​of the coccygeal-parietal size of the fetus and other indicators, which are also very important

Diameter of fertilized egg by week

When the fertilized egg has a diameter of 4 millimeters, this indicates a fairly short period of time - up to six weeks.

• Often they are fertilized egg size 4 weeks. Already at five weeks, the SVD reaches 6 millimeters, and at five weeks and three days the fertilized egg has a diameter of 7 millimeters.
• At the sixth week, the gestational sac usually grows to eleven to eighteen millimeters, and the average internal size of the gestational sac of sixteen millimeters corresponds to a period of six weeks and five days. At the seventh week of pregnancy, the diameter ranges from nineteen to twenty-six millimeters.
• Fertilized egg at 8 weeks increases to twenty-seven to thirty-four millimeters. At this stage, ultrasound can clearly examine the fetus.
• Fertilized egg 9 weeks grows to thirty-five to forty-three millimeters.
• And at the end of the tenth week, the fertilized egg measures about fifty millimeters in diameter.

As you can see, fertilized egg at 4 weeks It differs very much in size during the tenth week.

The question of how quickly the fertilized egg grows can be answered with confidence: until the fifteenth to sixteenth week, its size increases by one millimeter every day. Further, the diameter of the fertilized egg increases by two to three millimeters per day.

Average size of the fertilized egg in the first trimester of pregnancy

If, during an examination of a woman, an ultrasound machine detects a fertilized egg in the uterine cavity, the specialist will confirm the onset of pregnancy. Based on the size and shape of the formation, the doctor can determine the gestational age and possible problems gestation of the fetus. What does a fertilized egg look like? What should it be like at different times after conception?

The concept of the fertilized egg and its role in the body of a pregnant woman

The ovum is a structure that is formed after the fusion of an egg and a sperm, transforming into a fetus and amniotic membranes. First, 2 cells are formed, then 4, 8, etc. They transform into a zygote, then into a blastocyst, an embryo. On days 7–10, the formed fertilized egg implants into the uterine cavity.

The fertilized egg performs the following functions:

• preserves the developing fetus;
• provides the embryo with the necessary nutrition;
• supports blood circulation of the growing embryo at an early stage of development;
• secures the future fetus in the uterine cavity;
• forms amniotic membranes;
• creates the basis for the formation of the placenta;
• activates the production of the pregnancy hormone - hCG.

What does it consist of and what does it look like?

The fertilized egg looks like a small oval body. As you can see in the photo, the color of the formation is dark. This multi-component formation consists of the following elements:

• The chorion is the outer shell of the fertilized egg, which performs a protective function. It has villi that help attach the embryo to the uterine cavity. Subsequently, the chorion is transformed into the placenta.
• Amnion is the inner layer of the membrane of the fertilized egg. Produces a nutrient medium for the embryo - amniotic fluid.
• Yolk sac. Located between the above elements in the area where the future placenta fuses with the baby’s umbilical cord. Reminds me of a yellow pea. The sac provides nutrition to the embryo during the first stage of development.
• Embryo. In the first weeks it is not visualized. It can be considered after 6 weeks of pregnancy (we recommend reading:).

Diagnostic methods, indicators studied during ultrasound

There are several ways to determine the characteristics of the fertilized egg:

• Manual inspection. At this method the doctor calculates the size of the embryonic sac based on the size of the uterus. To determine the parameters of the uterus, the gynecologist palpates the woman’s vagina and abdominal cavity. The method has a large error, since the doctor cannot determine how many embryos are developing in the uterine cavity. If twins are expected, then the size of the reproductive organ is larger than in a singleton pregnancy.
• Ultrasonography. Ultrasound allows you to most reliably determine the parameters of the ovum. The membrane can be seen at 4 obstetric weeks of pregnancy, when it reaches a size of 1 mm. When the diameter reaches 3 mm, the yolk sac is visible. The study reveals: the average internal diameter of the fertilized egg (ID), its shape, place of attachment, the presence of detachment, the presence of an embryo, the size of the yolk sac.
• Blood test for hCG. HCG begins to be produced from the moment the embryo is implanted. When the embryo attaches to the uterus (on day 7), its level reaches 150 U/l. Subsequently, its concentration increases. Since there are norms for hCG and embryo size according to pregnancy, the size of the fertilized egg is determined. However, the necessary parameters are determined in this way only approximately, since hCG standards have a fairly large range (for example, at 3-4 weeks - from 1.5 to 5 thousand U/l), and with twins, the level of the hormone increases.

Parameters of the ovum are normal by week of pregnancy

The size of the fetal egg by week is of important diagnostic value until the 7th–10th week of pregnancy, when the embryo is poorly visible (see also:). After 12–14 weeks, it acquires the status of a fetus, and the placenta begins to form, their indicators are monitored. The fruit shell grows quickly. Until 15–16 weeks, it grows by 1 mm per day. For example, at 9 weeks its diameter is 35 mm, and at 11 it is more than 47 mm. The table shows what the SVD of the fetal egg should be from 4 to 13 weeks.

As can be seen from the table, from 1 mm in 14 days the diameter increases to 17–18 mm, and after another 7 days it reaches 20–24 mm. At the same time, the coccygeal-parietal size of the fetus is informative only from 8 weeks.

Possible deviations of the ovum at different stages of development of the embryo and fetus and their causes

Normally, the fetal membrane is convex and has clear edges. For a successful pregnancy, it must be attached to the upper part of the uterine cavity. If abnormalities are detected during the ultrasound, the doctor develops tactics for further pregnancy management. When planning events, the size of the fertilized egg must be taken into account.

Deviations from standard sizes, growth retardation

If at a period of 5–6 weeks, when the embryo is poorly visible, it is discovered that the fertilized egg is larger than normal, the woman may have twins. To confirm the assumptions, the expectant mother is given a referral for a re-examination after 7 days and hCG tests. However, if there is only one fetus in the shell, a large egg is a sign of pathology. A downward discrepancy is also a warning sign. The table shows possible reasons for deviations.

Particular attention is paid to the size of the fertilized egg after the IVF procedure. To monitor the dynamics, a woman after IVF is prescribed an ultrasound. Optimal is 28 DPP. At this stage, the fetal parameters should correspond to 5 obstetric weeks.

Non-standard shape of the fertilized egg

The fertilized egg acquires a non-standard shape when there is strong tension in the uterus. If the reproductive organ is tense, the fetal membrane becomes elongated or has a flattened shape. In this case, the doctor recommends taking measures to eliminate uterine tone. If there is nagging pain in the lower abdomen and bleeding, treatment is carried out in a hospital.

The non-standard shape of the fetal egg, coupled with developmental delays, indicates the onset of spontaneous abortion. In this case, it makes no sense to continue the pregnancy.

Incorrect position

Embedding of the embryo below the upper third of the uterus requires careful medical supervision. The low position of the embryo in the early stages does not pose a threat to pregnancy. There is a high risk that the fertilized egg will rise higher as the uterus grows. However, attachment to the cervix indicates the development of a “cervical” ectopic pregnancy. In this case, the embryo is removed.

The concept of an empty fertilized egg in the early stages

Until the 5th embryonic week, the embryo inside the fertilized egg is invisible. However, at 5–6 weeks from the moment of conception (or at 7 obstetric weeks), an embryo should be detected. If this does not happen, it is recommended to do an ultrasound a week later. If there is no embryo in the membrane at the 8th week of pregnancy, the formation of an empty egg in the uterine cavity is noted.

An empty egg is a round or disproportionately shaped bubble with liquid inside. It is formed in the following cases:

• For ectopic pregnancy (see also:). There can be two formations in the small pelvis: one fertilized egg is small and located in the uterus, and the other with an embryo develops outside the reproductive organ. If a pathological pregnancy is detected, both one and the second body are removed.
• With anembryony. It occurs due to genetic abnormalities during conception, as a result of infectious diseases suffered by a woman, endometriosis, endocrine and hormonal disorders. Pathology is eliminated by curettage or vacuum aspiration.