Determination of gestational age. When can pregnancy be determined by ultrasound: at what stage is the fertilized egg visible? Why is the gestational age calculated based on the first ultrasound?

Determining the due date is one of the most important indicators during pregnancy both for the expectant mother and for doctors. The fact is that by assessing the existing development indicators with the required ones, one can judge the delay in fetal development, which is often associated with circulatory pathologies, lack of nutrients and congenital anomalies.

How to determine the deadline?

You can determine the gestational age by ultrasound and menstruation, as well as during a gynecological examination . In the second case, a woman cannot always know exactly the date of sexual intercourse that led to conception or does not always monitor, and even more so, not all women undergo ultrasound.

• To calculate the week by dates, the so-called obstetric period is used. It is counted from the last date.
• Another guideline for calculating the timing of pregnancy is the first kicks of the fetus, which are approximately equal. An obstetrician-gynecologist can determine the timing of pregnancy using a gynecological examination, which is typical for, as well as by determining the abdominal circumference and standing height -.
• But with ultrasound diagnostics of pregnancy everything is more complicated. So, at what stage will an ultrasound show pregnancy? For the first time, the fetus can be detected already on the 5th day of delay. This date is approximately equal to . There is no way to see the fertilized egg earlier, since it has not yet been implanted in and is located in. In early diagnosis there are several nuances that are worth paying attention to.

The method of execution is, that is, the ultrasound sensor will be inserted into the vagina. It is not always recommended to use this method, especially if there is nagging pain in the lower abdomen and vaginal discharge. Many doctors do not recommend very early ultrasound diagnosis due to its low accuracy and impracticality.

• it is best to use a test, an examination by an obstetrician-gynecologist and a blood test for hCG. An ultrasound should be performed only if an ectopic pregnancy or hydatidiform pregnancy is suspected. If tests indicate a stop in fetal development, then... At this time, it begins to decline for the first time.
• As for the timing of diagnosis of ectopic pregnancy, it can be seen in the fallopian tubes on the 10-11th day of conception, and from the 20th day. But even here, not everything is so simple, due to the peculiarities of the localization of the fertilized egg, it may not be detected outside the uterus and then repeated visits to the ultrasound room will be required. In addition to ultrasound diagnostics, a blood test for hCG is also used.
• An ultrasound examination does not always determine the presence of a fertilized egg, although pregnancy can almost always be established by the tenth day. The reason may be, first of all, the above-mentioned pathologies; in addition to them, hormone-producing tumors, which are also diagnosed by ultrasound, lead to a positive pregnancy test result.
• Another disease that simulates pregnancy is a cyst.
• The next reason why pregnancy may not be detected is a medical institution that is not suitable for diagnosing pregnancy. This includes not only inappropriate or outdated equipment, but also incompetence of the specialists involved in diagnostics. At the same time, a transabdominal type of ultrasound can be chosen as a diagnosis, which is incorrect and greatly reduces the likelihood of establishing the fact of pregnancy and, even more so, establishing its timing.
• Well, the most banal reason is a miscalculation in the timing of which the ultrasound was scheduled earlier than the due date.

After the study, when ectopic pregnancy, tumors, cysts have been excluded and the fact of conception has been established, the doctor takes measurements of the fetus. Moreover, the earlier they were done, the more accurately the gestational age will be determined. Also, the result of such an ultrasound will confirm the development of the embryo or vice versa.

To clarify the fact of pregnancy, when the ovum is not visible on ultrasound, the corpus luteum is measured, the size of which will be higher than normal.

Accuracy in determining the gestational age using ultrasound

• In the period before 8 weeks accuracy of timing is approximately 1-2 days. This is due to the very similarity of fetal development in these weeks.
• In the second trimester, timing is assessed by measuring the distances between anatomical landmarks, as well as the size of the head, abdomen, etc. Special attention should be paid to the coccygeal-parietal index (CPI). It is a segment drawn between the coccyx and the head end. KTE allows you to determine not only the length, but also the weight. To assess it, special tables are used, which include the possibility of deviation of the indicator due to the constitutional characteristics of the child.
• The same methods can be used in the third trimester. But when assessing the fetus in the second and third trimester, the constitutional features of a particular fetus should be taken into account.

8 weeks pregnant fetal size ultrasound photo

Particular attention should be paid. The first allows you to create and evaluate a full-fledged 3D model, and the four-dimensional one allows you to evaluate everything in the same 3D, but, in addition, in real time. These methods allow, in addition to timing, to determine the presence of pathologies in the anatomy of the face, which are not always detected by conventional ultrasound.

Questions about determining the timing of ultrasound

• What age does ultrasound show? As stated above, there is an obstetric pregnancy period and an embryonic period. Obstetric is considered from the first day of the last menstruation, and embryonic from the day of conception. The ultrasound results are equated to the general norm, that is, they are equal to the obstetric period.
• Where is the best place to do an ultrasound during pregnancy in the 3rd trimester? This question most often arises among those who intend to perform a three-dimensional examination of the fetus according to indications or at their own request. An obstetrician-gynecologist who monitors the pregnant woman can suggest the location. In general, you can do it in .
• What to do if the ultrasound results do not correspond to the deadline? It is quite possible that errors were made in calculating the deadline earlier. If growth retardation occurs in the second half of pregnancy, then it may be necessary to perform

Modern women are very lucky. After all, relatively recently, pregnant women did not have the opportunity to see their baby before giving birth. With the development of medicine, this is now quite possible. At what stage does an ultrasound show pregnancy? This question worries every girl who has experienced a delay or has other symptoms that incline her to think about a possible case of fertilization. There is no point in immediately running to the doctors for the procedure; anyway, nothing will be visible yet. Therefore, you should be patient and wait a little. You can visit a gynecologist and ask him when an ultrasound will show pregnancy.

Embryo on ultrasound

Why do ultrasound examinations and what is its importance?

At the first signs of fertilization, the girl should contact the antenatal clinic to confirm her status and register. After all, medical supervision is very important during this period. For various reasons, pregnancy may not be confirmed: the test may show false data, or the cycle may simply go wrong for any other reason. The doctor, after examination, will confirm or deny this fact, but the presence of a fetus will definitely be shown by the first ultrasound procedure.

Why is it important to carry out this procedure after a delay? Let's look at the reasons in more detail:

• In case of prolonged absence of menstruation, it is possible to find out the true cause of the pathology if fertilization is not confirmed. After all, such a development of events can signal the development of a gynecological disease.
• In the early stages, pregnancy can be determined using ultrasound.
• Using an ultrasound, you can check whether the fetus is well attached, then assess its condition and rule out the development of any kind of anomalies.
• The procedure allows you to detect an ectopic pregnancy and protect the woman from the risk of harm to her health and life.
• Ultrasound examination is the only reliable source with which you can see fetal fading or a failed miscarriage.
• An ultrasound can save the child by showing in advance the threat of miscarriage due to increased tone or another reason. The doctor will prescribe the necessary therapy in a timely manner.

Ultrasound examination is an absolutely safe procedure, both for the unborn baby and for the young mother. All prejudices about its harmfulness are a complete myth.

At what period is ultrasound able to recognize the fertilized egg?

How many days after conception can you recognize the onset of an interesting situation? The egg is fertilized on the day of ovulation or a couple of days later. But for this it is important that the sperm reaches her. The egg travels through the fallopian tubes to the uterus, where it attaches to its mucous membrane. A woman feels a nagging pain in the lower abdomen, as before the onset of menstruation. From now on she is a future mother.

First diagnostic ultrasound to confirm pregnancy

An ultrasound to determine pregnancy will show an accurate result if you follow a number of conditions and recommendations:

• the procedure can determine pregnancy and the number of fetuses 90% accurately only at 10 weeks, so it is worth observing the timing of visits;
• absence of inflammation (due to swelling, the device will not distinguish a tiny embryo);
• selection of the most suitable type of ultrasound examination.

At what time can the origin of life be determined? This can be done in the first weeks of fertilization (at 3 weeks of pregnancy), but the result may not live up to expectations. Therefore, it is best to wait and carry out. Of course, if there are no special health reasons for a premature examination.

In modern medicine, the process of determining pregnancy in the early stages is represented by two options for ultrasound examination: transvaginal And abdominal. Using the first type, pregnancy can be determined as early as 21 days after conception. It is performed by inserting a special sensor into the vagina. This is a fairly accurate survey with the least amount of error. The second type of study is capable of determining pregnancy 5 weeks after fertilization.

What ultrasound should be done to determine early pregnancy? A gynecologist will answer a similar question after examining and assessing the mother’s health.

Transabdominal and transvaginal ultrasound sensors

How to prepare for the pregnancy detection procedure?

Determining pregnancy by ultrasound requires that certain rules be followed in order for the results to be reliable. Gases in the intestines interfere with any research, so it is worth excluding legumes and other gas-forming foods from the diet. At least two days before the procedure.

When a transabdominal examination is ordered, the bladder must be filled. It is advisable to drink a sufficient amount of water three hours before the procedure, if the woman is able to tolerate that much. Because of this, discomfort may occur during the examination. It is impossible to accurately determine the gestational age using an ultrasound with an empty bladder.

If you are scheduled for a transvaginal procedure, have a bowel movement and avoid sex a couple of days before the test.

Is it necessary to conduct an ultrasound examination in the early stages?

Ultrasound shows pregnancy starting from 3 weeks. However, if there are no special appointments, then it is not worth carrying out the procedure at such an early stage at the individual request of the expectant mother. How to determine the gestational age, how many weeks have passed since the day of conception, if you do not carry out the procedure? The doctor will help the girl figure this out during an examination in a gynecological chair and based on test results.

Pregnancy should not be checked using a transvaginal ultrasound if a woman is bothered by aching pain and cramps in the lower abdomen, as well as during a period when periodic brown or red discharge is noted. Is it possible to use this method to detect the presence of a fetus in the early stages of pregnancy? Yes, this type of study determines conception quite accurately, but doctors often talk about the possible risks of damage to the embryo. Therefore, the procedure must be performed by an experienced doctor.

Can a doctor make a mistake?

It is possible to see pregnancy in the early stages, but sometimes an inexperienced diagnostician can confuse it with a hematoma or other neoplasm. Determining the gestational age or sex of the child can be erroneous. The reasons for this are the following:

• short period of time;
• the presence of hematomas and other formations;
• old, poorly functioning equipment;
• non-professional physician conducting research.

Error cases are quite rare. Almost always, ultrasound can detect the presence of a fetus. How many days later can the procedure be repeated? A specialist will inform you about this at your appointment.

At what stage will an ultrasound show pregnancy? First planned The procedure is carried out at the 10th week of an interesting situation for a representative of the fairer sex. But the fertilized egg can be seen after 5 days of absence of menstruation. What kind of ultrasound is done to detect conception? The most accurate method is transvaginal, but it is carried out only in the absence of contraindications.

Determining the gestational age by ultrasound is an important issue for every expectant mother.

Based on this, the extent to which the baby’s development corresponds to gestational age is assessed, and the approximate date of birth is calculated.

Obstetricians judge whether the fetus has enough oxygen and nutrients and determine some issues related to pregnancy and childbirth based on this parameter.

How to determine gestational age using ultrasound

1. According to the woman's calculations. So, she may not know the date of ovulation (based on basal temperature or folliculometry, which is performed as a standard gynecological ultrasound) or the date of the sexual intercourse that led to conception. But all women know the date of the last menstruation, and from it the main calculation is made, which is called the obstetric period. Later, at 16-20 weeks, the date of the first noticeable motor activity of the fetus will also be a reference point.
2. According to the gynecological examination - in the first trimester, according to the circumference of the abdomen and the height of the uterine fundus - in the second half.
3. Ultrasound diagnostics significantly helps determine the period. We will look at it below.

When will it be known for sure that you are expecting a child?

At what stage will an ultrasound show pregnancy? Immediately after unprotected sex, even if it was oriented for ovulation, the fertilized egg will not be visible. You can see the embryo for the first time 5 days after the delay. But there are several nuances here:

1. early diagnosis should only be done transvaginally, that is, by inserting a sensor into the vagina
2. transvaginal examination is dangerous if conception is desired, but there is bleeding in any quantity and pulls in the lower abdomen
3. Ultrasound diagnosis of pregnancy in the early stages should be carried out only when indicated: suspected ectopic pregnancy or hydatidiform mole. It has not been proven that ultrasound will be harmless at the beginning of fetal development.
4. if there is a suspicion that the embryo is not developing (that is, the uterus is not enlarging according to the results of a gynecological examination), an ultrasound at short notice is done no earlier than 5 weeks. Only then and only the vaginal sensor will be able to see how the embryonic heart makes its first contractions.

An ultrasound detects pregnancy at 3 weeks or more. But transvaginally sent ultrasound will detect ectopic implantation of the embryo already on the 10-12th day of conception (abdominal examination - on the 20th day of conception). In addition, a blood test for hCG helps in differentiating between ectopic and normal embryo implantation.

Although it is known at what stage an ultrasound shows pregnancy (from the 10th day of delay - in almost 100% of cases), the device did not see it specifically for you, this may be as a result of:

1. incorrect calculation of gestational age, that is, you went to the study early
2. the study was carried out “through the stomach”
3. quite old ultrasound scanner
4. that you underwent the study in a multidisciplinary center and not in a specialized clinic
5. the doctor’s qualifications to determine pregnancy so early were insufficient
6. the test is false positive, but due to a corpus luteum cyst or other pathology
7. there may be a miscarriage during this period, mistaken for menstruation, then the hCG, which created the second strip, simply has not yet returned to normal.

What are the benefits of early research?

Ultrasound at a short term can show the fetus if the hCG level is 1-2 thousand mU/l.

It helps the obstetrician with the following:

1. making a diagnosis of “Ectopic embryo implantation”
2. establishing the very fact of successful conception, clarifying the location of the fertilized egg
3. finding out the reason for the delay of menstruation in the absence of a positive test (“two stripes” can cause uterine fibroids, ovarian cysts)
4. calculating the gestational age using ultrasound: the earlier the fetal egg is measured, the more accurate this figure is, since at the beginning of pregnancy the development of the embryo does not yet have individual characteristics.
5. determining the number of fruits (but this is not very accurate)
6. determining the threat of miscarriage

If the study was done early enough to visualize the ovum, an “interesting position” can still be suspected by the presence of a corpus luteum measuring 16-25 mm in the absence of menstruation.

Accuracy of Gestational Age Calculation

Determining the gestational age up to 8 weeks is based on measuring the length of the embryo. Right now, ultrasound determines the period exactly up to 1-2 days, since during this period almost all embryos develop in the same way. 3D ultrasound is not performed so early during pregnancy, only in the second half.

In the second trimester and later, the number of days is determined by comparing such dimensions as head circumference, coccygeal-parietal distance, chest diameter, and length of tubular bones.

Here, the accuracy of ultrasound is much less, since the comparison is with the average standards for a given population. Each child grows and develops individually; in addition, growth occurs in waves. A 4D ultrasound during pregnancy will help to assess the correct development of the fetus in the second half.

How is gestational age calculated?

Specially compiled measurements and tables of standard indicators will help you calculate the gestational age using ultrasound. Thus, up to the 12th week, measurements of the internal diameter of the fetal egg (ID) are used, and from the 7th week the parameter of the coccygeal-parietal distance (CPR) is added to this indicator.

For example, for 7 weeks exactly the SVD indicators are 7-19 mm, and the CTE indicators are 8-11 mm. Already at 7 weeks and 1 day, SVD is 8-20 mm, and CTR is 9-12 mm.

Table of pregnancy dates according to ultrasound

Here you can see when an ultrasound can detect pregnancy - from the 5th week.

Evaluation of the fetus according to such parameters as indicated in the table is called fetometry. From the 3rd month, “age” is calculated using fetometry:

The most common questions about fetal ultrasound measurement

What stage of pregnancy does an ultrasound show?

There are two main ages of the fetus:

1. obstetric – determined from the first day of the last monthly bleeding (the date of birth for this period is calculated as follows: from this date minus 3 months and plus 7 days)
2. embryonic – from the moment of conception (this date is taken as the day of ovulation). It turns out shorter than the first by 2 weeks.

Ultrasound does not directly calculate gestational age. With the help of this study, an analysis is made of how many weeks (obstetrics are taken as a basis) the fetal parameters correspond to.

Pregnancy is a very dynamic process during which the growth and development of the fetus occurs, and restructuring occurs in the woman’s body in accordance with the stage of its development. Therefore, correct determination of the gestational age is very important for understanding the changes that occur in each period gestation(pregnancy).

Information To correctly determine the duration of pregnancy, information about the first day of the last menstruation, from which it is calculated, is important. This approach is valid for a regular menstrual cycle.

Fertilization usually occurs after ovulation(the release of the egg from the ovary, that is, in the middle of the cycle), therefore this definition of the period is somewhat averaged and differs from the true one by an average of 14-16 days. But since in most cases the exact date of ovulation is unknown (with the exception of in vitro fertilization programs), counting from the first day of the last menstrual period is most often used.

By date of first movement

You can also take into account the date of the first fetal movement. For primiparous women this is usually about 20 weeks, for multiparous women - . But fetal movements are a rather subjective sign (especially in the early stages it can be confused with intestinal function), so it can only be used as an additional one.

Besides data medical history(a set of information obtained by interviewing the patient) when establishing the gestational age, one should focus on objective data obtained during examination, that is, the size of the uterus and the position of its fundus, as well as the results obtained during an ultrasound examination.

Determination of the period based on the height of the uterine fundus

The size of the uterus and the height of its fundus at different stages of pregnancy

From the very beginning of pregnancy, the uterus begins to gradually grow and by each month it should have a certain size during the normal development of pregnancy:

• By the end of pregnancy, the uterus reaches the size of a chicken egg;
• The size of the uterus corresponds to the size of a goose egg, which is clearly determined by vaginal examination;
• The uterus is determined at the level of the border of the upper edge of the pubic arch;

• The fundus of the uterus is located in the middle of the distance between the navel and the pubis (4 transverse fingers above the pubic symphysis - the articulation of the pubic bones);
• By pregnancy, the fundus of the uterus is set 2 transverse fingers below the navel;
• The fundus of the uterus is at the level of the navel;
• The bottom of the uterus is determined 2-3 transverse fingers above the navel;
• The fundus of the uterus is installed in the middle of the distance between the navel and the xiphoid process of the sternum;
• This level reaches the xiphoid process and costal arches;
• The fundus of the uterus lowers somewhat due to the expansion of the lower segment (the body is preparing for childbirth) and the lowering of the presenting part (usually the head) and is located in the middle of the distance between the navel and the xiphoid process.

This parameter should be assessed only in conjunction with the others, since the height of the uterine fundus increases in the presence of a large fetus, multiple pregnancies, or in case of abnormal fetal position, and decreases in the case of a small fetus, or with a low standing of the presenting part of the fetus (if there is a threat of miscarriage). Also, the increased size of the uterus can, especially in the early stages, imitate the presence of myomatous nodes, hydatidiform mole and other pathology.

How to calculate gestational age using ultrasound

Ultrasound examination () is of great help in determining the duration of pregnancy. In the early stages, when the embryo is not yet determined, the period is set based on the size of the fertilized egg.

Indicators of the average internal diameter of the ovum

From the moment when the embryo begins to be determined in the fertilized egg, the gestational age is determined based on the size coccygeal-parietal size of the embryo/fetus(this is the maximum distance from the head end of the fetus to its tailbone). This method is more accurate than determining the period by the diameter of the fertilized egg.

Estimation of gestational age based on embryo/fetus

In the second half of pregnancy, the gestational age is determined based on several measurements:

• Biparietal size of the fetal head;
• Fetal abdominal circumference;
• Length of the femur.

The period established on the basis of ultrasound examination is correlated with the menstrual period and the data of objective research.

Duration of pregnancy and determination of the date of birth

The average length of pregnancy is 280 days, which corresponds to 40 weeks. It is impossible to determine the exact date of birth for each specific pregnancy. Therefore, a term birth (that is, a full-term birth) is considered to be a birth between 37 and 42 weeks of pregnancy. Moreover, at 37 weeks the baby may not yet be ready for extrauterine life, but the birth will not be considered premature. And at 41-42 weeks the baby may be born with signs of postmaturity.

How to calculate your due date

The estimated due date can be determined in the following ways:

• On the first day of the last menstruation: add 280 days to it and get the due date corresponding to 40 weeks of pregnancy. It’s easier to subtract 3 months from the first day of the last menstruation and add 7 days (For example, the first day was March 15, subtract 3 months - December 15 and add 7 days, we get the expected date of birth - December 22);
• By ovulation: from the first day of expected but not occurring menstruation, subtract 14 days and add 273 days. This method is valid for regular menstruation;
• By exact date of fertilization(more often used for in vitro fertilization - 3 months are subtracted from the date or 273 days are added);
• According to the gestational age established at the first visit to the antenatal clinic(more precisely when registering up to 12 weeks);
• By date of first movement: for primiparous women, 20 weeks are added to the date of the first movement, for multiparous women – 22;
• By date of prenatal leave(at 30 weeks, 10 weeks are added to this number);
• According to ultrasound data(the most accurate for determining the period is the first screening ultrasound at 10-14 weeks, since the fetus does not have characteristics related to race, gender, etc.);
• According to the degree of maturity of the cervix: This method is based on studying the cervix during vaginal examination. In this case, you can determine whether the cervix is ​​mature or not (that is, determine its readiness for childbirth), but not indicate the exact date.
• According to colpocytological test. This method is based on taking material from the cervix and examining it under a microscope to determine the ratio of different cells. Changes in the composition of cells can be used to judge the expected date of birth.

Today, there are many special obstetric calendars that, based on the first day of the last menstruation, make it possible to determine the duration of pregnancy, as well as the expected date of birth.

There are times when a woman cannot remember exactly when she had her last menstruation. Therefore, the most accurate way to determine the duration of her pregnancy is only with the help of ultrasound.

Among all the modern diagnostic methods that determine the gestational age, only ultrasound examination makes it possible to accurately determine the age of the fetus.

Why do you need to know the exact date of conception? The most important reason for this is a woman going on maternity leave.. The expectant mother is sent to it at 7 and a half months. To avoid any difficulties, you should have a doctor’s certificate indicating the exact period of the woman’s interesting situation.

If a woman goes for an ultrasound examination for the first time in order to determine the exact date of birth in the last trimester, then the possibility of error will increase significantly. This is due to the fact that the development of all children is different. Consequently, by the time she needs to go on prenatal leave, it must be known exactly how many weeks she is before giving birth.

Determining the “age” of the fetus using ultrasound

The question of how long a pregnancy is is of concern not only to expectant parents. For doctors who are responsible for the health of a pregnant woman and her unborn baby, it is even more important. A specialist in an antenatal clinic needs this data to determine whether the fetus is developing correctly and whether the entire process of developing a new life is proceeding normally.

How is the gestational age determined? How accurately does this data reveal the birth of new life? One way to determine this can be the words of the woman herself. Every representative of the fair half knows how many days have passed since the last menstruation and almost always remembers exactly the first day of the last menstruation. It is from this day that the doctor begins to count the duration of her pregnancy. This is the so-called obstetric method of determination.

If a woman was planning to become a mother and measured basal temperature or folliculometry, then the data she received can be very helpful to the doctor.

If conception is suspected, the woman comes monthly for an appointment at the antenatal clinic, where the doctor examines the woman, and if the uterus is enlarged, it is assumed that pregnancy has occurred. The entire period of gestation for the expectant mother is determined by the period of her interesting position according to the height of the uterus (for this purpose, the volume of her abdomen is measured), the size of the pelvis is also important.
But all these indicators are not considered one hundred percent accurate.

A more accurate method for determining the period of an interesting position is ultrasound examination. At twelve to fourteen weeks, all women preparing to become mothers are sent for an ultrasound. At this time, it is possible to see whether the fetus is developing correctly. When determining the period in the first three months, it is not always possible to see many important details; diagnosis in these cases is carried out strictly according to indications.

Until the tenth week, the period is determined by the size of the embryo. This is due to the fact that in the first months all embryos develop equally. During this period it is difficult to make a mistake; the error usually does not exceed several days. And in the second trimester, development becomes individual for each individual fetus.

If you go for ultrasound diagnostics immediately after fertilization, then even the most cutting-edge device will show absolutely nothing. You can contact a specialist no earlier than a week after the delay. First, the woman must be examined by a gynecologist. Only he can decide whether there is a need to undergo an ultrasound at such an early stage.

The fact is that transabdominal ultrasound examination at this stage will not give any results. In this case, the diagnostic procedure is carried out using a special sensor, which is inserted into the vagina. Only in this way is there a chance to examine the embryo.

At such early stages, transvaginal examination is carried out only in cases of urgent need, for example, there are serious suspicions that the fetus is not developing in the uterus. Also, diagnosis and determination of the fetal term in the early period using ultrasound are necessary during in vitro fertilization, when it is necessary to check whether it was successful.

It must be remembered that pregnancy can be easily interrupted in the first months, so such procedures should be approached with caution if you want to give birth to a child.

So when can you go for an ultrasound examination for a reason? When can the “age” of the fetus be accurately determined? How many times should a woman go for ultrasound diagnostics to determine her due date? If in the first week after fertilization it is still impossible to see anything for sure, then already in the third week you can determine pregnancy with one hundred percent accuracy.

Why is ultrasound diagnostics carried out at various periods to determine the lifespan of the embryo and fetal development:

• in the fifth to eighth week, an ultrasound confirms the presence of the embryo in the uterus and where it is attached. During this period, it is already possible to calculate his heart rate and visualize how he moves. Determine the thickness of the layer of the uterus that will subsequently become the placenta;
• in the tenth to twelfth week you can accurately determine the “age” of the fetus and whether it is developing correctly. At this stage, the due date is determined. The doctor assesses the width of the collar zone. At this time, most of the possible pathologies and developmental anomalies are already visible. If its indicators are within the normal range, this indicates normal development of the fetus in genetic terms;
• The twenty-second to twenty-fourth week is the best time to exclude malformations and calculate the day of birth. The volume of water around the unborn child, development and size of the fetus are also assessed.

If any abnormalities are suspected, the woman is referred for genetic consultation. If the unborn baby can be examined from all sides, the gender can be determined with one hundred percent accuracy;

• The thirtieth to thirty-second week is the most suitable period for assessing the activity of movements of the unborn child. During the study, you can see whether the baby is developing correctly and whether he is mobile. It is also determined whether the blood flow to the placenta and the main reproductive organ of the expectant mother is intense. If the baby is entwined with the umbilical cord or is positioned incorrectly in the uterus, the specialist may prescribe an additional ultrasound before the birth. At this time, they decide which type of delivery is most suitable in a particular case (the woman herself will give birth or the child will be born by caesarean section).

Accuracy of ultrasound diagnostics in determining gestational age

If a woman has a regular menstrual cycle, that is, twenty-eight days of the calendar, then the data on the expected period of the fetus, obtained by ultrasound, coincides with the first day of the last menstruation. If these indicators still do not coincide, then you should rely on ultrasound diagnostics. This is due to the fact that fertilization often occurs fourteen days after the first day of the last menstrual period.

It happens that the determination of the period of an interesting position based on the size of the uterus does not coincide with the data obtained from an ultrasound examination. This depends on the individual characteristics of the pregnant woman, but this information is still taken into account. Also, the development of the fetus itself may not correspond to the usual time characteristics. In this case, ultrasound diagnostics can put everything in its place. These discrepancies can be fourteen days in the thirtieth week and 21 days in the 36th to 40th weeks.

Nature is more cunning than all possible calculations, so even ultrasound cannot show one hundred percent accurate date of birth. Even if the expectant mother knows when fertilization occurred, an ultrasound examination provides data that is fourteen days ahead of this date. It turns out that ultrasound cannot give the exact date of birth, but it calculates the due date more accurately than all other methods.

The day of birth is calculated based on 38 weeks. But a normal pregnancy lasts 38-40 weeks, that is, again, plus or minus two weeks: there are women who give birth at 39 or 40 weeks. Gestation lasts forty weeks according to ultrasound, 38 according to gynecologist estimates. Normal birth occurs at 40 weeks according to ultrasound scan or on the first day of the last period - ten days after the date. Even if the due date is calculated correctly, birth may occur earlier due to medications, illnesses of the expectant mother, injuries and stress.

A pregnant woman should be examined with ultrasound four times during her entire happy period. If there is a suspicion of spontaneous abortion, the procedure is performed more often. But isn't ultrasound harmful for a woman and her unborn baby?

The harm from ultrasound has not been proven, but there is also no data on its complete harmlessness. Not a single newborn baby suffered from the ultrasonic waves to which it was exposed in the womb. But no one knows what will happen to these children and their descendants in thirty, fifty or more years. Therefore, it is not recommended to increase the number of visits to the ultrasound diagnostic room without serious reasons. It is necessary to immediately appear for a diagnostic procedure, which is carried out using ultrasonic waves, if the expectant mother’s well-being has sharply deteriorated, bloody discharge from the vagina has appeared, and there has been no movement for a long time.

For what reasons may an ultrasound not show an embryo in the uterus?

It is not uncommon for a woman to experience all the subjective signs of pregnancy with a positive test, but an ultrasound examination did not confirm the fact of future motherhood.

This can happen for the following reasons:

• if a woman came for a diagnostic procedure earlier than necessary;
• the study was carried out transabdominally;
• outdated or insufficiently accurate ultrasound machine;
• insufficient qualifications of the doctor who performed the diagnosis;
• at the time of the procedure, a spontaneous abortion had already occurred (which is not uncommon in the early stages).

It is worth considering one more important detail. The viability of sperm is 72 hours. Therefore, it is impossible to say exactly when fertilization occurred. This means that during ultrasound diagnostics the gestational age will be determined with an error of two to three days.

It should be remembered that you should not take risks and undergo diagnostics in a multidisciplinary clinic where there is no high-quality equipment and competent specialists. It is better to contact a specialized institution, where research is carried out by experienced specialists using modernized and precise equipment.

It is equally important to consider that the question of how many times you need to go for an ultrasound examination should be decided only by a doctor.

A woman may have suspicions about a possible “interesting situation” long before her next menstruation is missed. Modern test strips can determine the content of the specific hormone hCG in the urine already on the first day of the delay, and some even several days before it. Whatever the test result, a woman wants to make sure she is pregnant as early as possible. This article will tell you when the baby can be seen for the first time on an ultrasound.

Minimum terms for determination

After conception has taken place, intensive processes begin inside the expectant mother, which she most often is not aware of. On the very first day, the fertilized egg divides and moves through the fallopian tube, where conception took place, into the uterine cavity. This journey lasts about four days. It is no longer a set of individual cells that descends into the uterus, but a blastocyte - a ball-shaped formation. It penetrates the lining of the uterus. This is implantation. This happens 6-7 days after fertilization, and sometimes a woman feels implantation by slight pulling sensations in the lower abdomen.

The earliest symptom of pregnancy is sometimes the so-called implantation bleeding - a few drops of bloody or bloody discharge at the time of blastocyte implantation into the endometrium. This doesn't mean it's time to run out for a test or sign up for an ultrasound.

The test strips react to the formation of the so-called pregnancy hormone - hCG, but it is just beginning, the level of the hormone is below the control level of the sensitivity of the test strips. But a blastocyte cannot be seen on an ultrasound - its size is only 0.2 mm.

There is no placenta yet; nutrition for the embryo is “supplied” by the mucous membrane of the uterus. But from the very first day after attachment, the baby begins to produce hCG, this hormone gives the entire female body commands of mass “mobilization”. The restructuring of all systems of the female body begins in order to create the most comfortable conditions for the further growth of the child.

In two weeks after conception, the child grows up to 1 mm, menstruation begins to be delayed, and during this period pregnancy can already be determined with a high probability by the level of hCG in the blood (if a woman takes a blood test from a vein), test strips also begin to “strip.” However, the ultrasound will still not please the woman; the pregnancy is not yet visible.

In 3 weeks after conception (this is the fifth obstetric week, which is counted from the first day of the last menstruation), the baby’s size reaches 4 mm. His neural tube is formed, and the formation of the placenta begins. The embryo takes on an oval appearance - a fertilized egg appears. Exactly 3 weeks after conception, the formation of the brain and spinal cord begins, and the heart of the embryo begins to beat.

It is a week after the start of the delay (this approximately corresponds to the 21st day of embryo development or a full 5 obstetric weeks) that the embryo can be seen for the first time using ultrasound diagnostics. True, this possibility depends on many factors.

• A woman should not have polyps or diseases of the uterine mucosa. If such pathologies exist, the doctor may confuse the fertilized egg with a fragment of a polyp, and pregnancy will not be confirmed.
• The scanner must have good resolution; pregnancy can be determined at such a minimum period only with modern, good equipment and, of course, with the help of an experienced and qualified doctor.

Indications for examination

If there are no periods, the test is “striped” or it does not show an interesting position, then 10 days after the start of the delay, in any case, you should contact an antenatal clinic. An obstetrician-gynecologist at this stage can manually determine a slight enlargement of the uterus when examining a woman.

An ultrasound scan 10 days after the delay gives fairly accurate indicators of the presence, absence and characteristics of the embryo. This does not mean that all pregnant women without exception at such early stages should go to ultrasound diagnostic rooms and do ultrasounds as much as they want. The effect of ultrasound on the embryo is not considered harmful, but it cannot be called beneficial either, it has not yet been sufficiently studied.

There are certain indications for which a doctor will recommend a woman to undergo an ultrasound procedure at such a short time:

• The delay is accompanied by unpleasant, painful sensations, there is discharge that is not menstrual;
• Previously, the woman had ectopic pregnancies, early miscarriages;
• If there is a delay, the test shows a positive result, and the size of the uterus and the characteristics of the organ during palpation do not tell the obstetrician about the onset of pregnancy;
• If the woman has previously had uterine surgery, including cesarean section;
• If a woman does not remember the date of her last menstruation.

Diagnostics with an ultrasound scanner in these cases will make it possible to determine whether implantation has occurred in the uterine cavity, whether the woman is developing a tubal (ectopic) pregnancy, and also to determine whether there is a detachment of the ovum if abnormal discharge occurs. It is in the early stages that the gestational age can be determined with an accuracy of one day., because in the embryonic period all embryos grow at approximately the same speed.

For women who have undergone surgery on the uterus, an ultrasound will help them find out what condition the postoperative scar is in, and whether the fertilized egg has become attached to the scar area. If a woman does not have any concerns or a complex medical history, then there is no urgent need for an ultrasound, and the expectant mother will be able to look at her baby for the first time at 11-13 weeks, when the doctor gives a referral for the first prenatal screening.

How is an ultrasound done?

To determine pregnancy, two types of ultrasound examination are used - transvaginal and transabdominal. In the first case, the doctor examines the uterine cavity and its contents with a vaginal sensor. In the second case, the inspection is carried out with a sensor through the abdominal wall. For the most part, doctors prefer the first method when it comes to early pregnancy. Through the vagina it is much easier to see the embryo and its structure.

An abdominal ultrasound of the pelvic organs is recommended to be performed with a full bladder, a transvaginal ultrasound with an empty one, and it is better to take care in advance that the intestines are not distended from gases. To do this, a few hours before going to the doctor, it is advisable for a woman to take Espumisan or Smecta.

It should be noted that using the transvaginal method, pregnancy can be seen earlier than the transabdominal method, by several days. Thus, a vaginal sensor and a good specialist in addition can tell a woman about her “interesting situation” already on the 5-6th day from the day of the delay, and a scan through the abdomen may not show pregnancy even on the 8-10th day. The procedure is painless, non-hazardous for the woman and baby, and lasts no more than 5-7 minutes.

Transcript of the first ultrasound

At the very first ultrasound examination to determine pregnancy, the diagnostician will be able to detect an echogenic formation. This is the fertilized egg. Its size will indicate the exact stage of pregnancy. The doctor will also determine the size of the yolk sac, the position of the fertilized egg, the thickness of the endometrium, and rule out inflammatory processes in it, as well as the presence of cysts, polyps and other unwanted formations. The dimensions of the fertilized egg and the timing table are presented below.

Obstetric period (from the date of the last menstruation)

Diameter of the fertilized egg (in mm)

KTR (distance from the coccyx to the crown), mm

BDP (biparental size), mm

Diameter of the yolk sac, mm

Are errors possible?

The ultrasound diagnostic method is considered one of the most accurate for determining pregnancy in the early stages, but you should not assume that its accuracy is 100%. In gynecology, the accuracy of this test is estimated at approximately 90%. In early pregnancy, accuracy decreases to 75%. A doctor is, first of all, a person, and not a machine with a program embedded in it. He has the right to make mistakes, especially if a woman has problems with the health of her reproductive system. Thus, a doctor may confuse uterine fibroids with pregnancy in the early stages if the woman had not previously been diagnosed with fibroids and only learned about its presence through an ultrasound. A cyst or polyp can be confused with a fertilized egg, since a cyst is also an echogenic formation.

If a woman had late ovulation, then the pregnancy a week after the delay may not be detected at all by an ultrasound diagnostic specialist, since the fertilized egg later descended into the uterus and is not yet visualized. Naturally, the doctor will write in the conclusion that no signs of pregnancy were found, but after 7-10 days, during a repeat examination, he will be able to determine both the fertilized egg and its structure. Only the size will help you understand that ovulation was indeed late.

Common Questions

On the Internet, inexperienced pregnant women and those who are still dreaming of an “interesting situation” ask many questions regarding the earliest diagnosis. It is worth talking about the most common situations in more detail.

The pregnancy test was positive, but the ultrasound was not.

There may be several reasons for this. First of all, one should not rule out that the test turned out to be defective; this happens, and quite often, especially when it comes to inexpensive test strips, which are sold on almost every corner. In their desire to see the two treasured stripes, some ladies go too far, starting to look for “ghost” stripes on the dough strips. If they find it, they automatically begin to consider their test positive, although in reality there may not be a pregnancy.

If the test still did not deceive, then the reason for the negative conclusion of the ultrasound diagnostic doctor may be that the woman went to the doctor too early, and the fertilized egg is not yet visible. The device itself may be outdated, with low sensitivity and poor resolution. The reason for the absence of signs of pregnancy on ultrasound may be late ovulation, the presence of an inflammatory process in the uterine cavity, and, of course, insufficient qualifications of the doctor.

The pregnancy test was negative, but the ultrasound was positive

There may also be plenty of reasons for this situation. Firstly, the woman could have carried out the test at home with an error, the test could have been defective or expired, and it is also possible that it was carried out too early, when the level of the hCG hormone in the urine was still insufficient for the test to respond brightly. second stripe.

Ultrasound diagnosis in this case is rarely premature, since a woman, after a negative home test, does not rush to the doctor, patiently waiting for the onset of a late period. After one and a half to two weeks of delay When the lady finally goes to the doctor, the pregnancy is already clearly visible on an ultrasound. Therefore, ultrasound results should be considered more reliable than home test results. In doubtful cases, you can donate blood for hCG to obtain even more accurate data.

How to calculate gestational age using ultrasound?

To do this, you can use the table above. If greater detail of the period is required, use a table of correspondence of the period, accurate to the day, to the average internal diameter of the fertilized egg (SVD). A table of pregnancy periods in accordance with the SVD is given below.

The value of the average internal diameter of the ovum

Every pregnant woman is concerned about the question of how accurately the gestational age can be determined by ultrasound. After all, based on this indicator, the doctor will compare how the gestational age corresponds to the development of the child, whether the baby has enough nutrients and oxygen, and also evaluates many other parameters that may affect the management of pregnancy and the method of the upcoming delivery.

Why is it necessary to determine the gestational age by ultrasound?

It is very rare that a woman knows exactly the date when the baby was conceived in her belly. Therefore, obstetricians-gynecologists, in order to calculate the expected date of fertilization as accurately as possible, use several methods, both “old-fashioned” and modern ones - determining the gestational age using ultrasound.

How can a gynecologist find out the date of conception of a child:

• According to a woman. Almost every woman knows the date of the first day of her last menstruation, so it is from this day that in most cases the doctor begins to “count down” the pregnancy; this method of determination is called obstetric. Also, the expectant mother can help the gynecologist more accurately determine the date of conception if the pregnancy was planned and the woman underwent a folliculometry procedure or measured her basal temperature.
• According to gynecological examination. Carrying out an examination at the beginning of pregnancy, the doctor determines the size of the mark, and from it suggests the period of the interesting position. Later, when the belly grows, the gynecologist determines the height of the uterus, the circumference of the abdomen, and from these parameters calculates the gestational age.

The methods listed above for determining the time of conception of a child are not 100% reliable, therefore, to clarify the date of fertilization, the gynecologist needs to know what stage of pregnancy is determined by ultrasound.

How to determine gestational age using ultrasound

Despite the fact that technology has stepped far forward, and modern ultrasound machines have become highly accurate, they can detect the conception of a new life in a woman’s stomach no earlier than five days after a missed period. That is, an ultrasound shows pregnancy at a period of three weeks. But gynecologists do not recommend that women undergo this type of diagnosis at such an early period just to make sure that a child has been conceived. The exception is when a woman has already had an ectopic pregnancy, and the doctor directs her to make sure that the fertilized egg was implanted in the uterine cavity and not in the lining of the fallopian tube.

In order to be able to determine the duration of pregnancy with maximum accuracy or to promptly identify the development of pathological conditions, gynecologists recommend that women undergo transvaginal examination. With this type of diagnosis, the sensor is inserted into the vagina, so it is located much closer to the organs being examined, which makes this ultrasound more reliable and informative.

Regardless of which sensor is used to conduct the study, the sonologist (a specialist who performs ultrasound) determines the gestational age based on the size of the fetus. The sonologist has special tables with standard indicators. The doctor compares the data obtained during the examination with the data in the table, and based on them makes a conclusion about the gestational age.

Until week 10, the determination of the period is based on calculating the length of the embryo. At this stage, the diagnostic error is minimal, no more than 1-2 days. Since in the first months after conception, all embryos develop at the same speed. But starting from the second trimester of pregnancy, when the little person’s body has already formed, the sonologist takes measurements of the coccygeal-parietal distance, head circumference, length of tubular bones, chest diameter, and based on these data gives a conclusion about the “age” of the baby. After the 12th week, the accuracy with which the duration of pregnancy is calculated decreases, since each child develops and grows individually, depending on which genes he inherited from his parents. Therefore, the gynecologist, when sending a woman for an ultrasound in the second or third trimester, takes this error into account. And if the size of the baby indicated in the sonologist’s conclusion is more or less than the norm, but equal to the corresponding values ​​​​of the previous or next week of pregnancy, then this is considered acceptable.

When conducting diagnostics in early pregnancy, doctors estimate the period using the following table.