The fetus is 4 mm what is the gestational age. Fertile egg. Ultrasound examination at a short gestation period

Ultrasound in obstetrics is the best research method due to safety and high information content. At the present stage, it is possible not only to visualize the fetus, but also to assess the structure and development of its organs, to identify malformations in the supply vessels.

New directions are the use and to obtain a clear image of the external parameters of the child a. Such a study is of particular interest to future parents.

If there are no special indications, ultrasound is performed during maternity periods once in each trimester of pregnancy:,. Research in these periods has its own goals and objectives. So, with ultrasound in the first trimester, the presence of pregnancy and the fact are established, its ectopic location is excluded, abnormalities in the development of the fetus are detected, and the exact gestational age is also determined.

To determine the gestational age with ultrasound, the fetus is important. This parameter is the main one when setting the term, but it is informative only in the first trimester of pregnancy.

This is due to the fact that in the early stages the correlation between the length of the fetus and gestational age is pronounced and does not depend on pathological processes. When conducting an ultrasound examination several times in the first trimester, it allows not only to determine the gestational age, but also to assess the dynamics of growth, to suggest the possibility of developing a large fetus or intrauterine growth retardation.

The fetal CTE is the longest fetal length that does not include limbs and the yolk sac. The measurement is made with the transducer positioned longitudinally when the maximum length of the embryo is taken out. If the fetus is actively moving during the ultrasound examination, the image with maximum extension is selected to determine the CTE of the fetus.

It is also a useful technique to carry out a three-fold measurement of the CTE of the fetus with the choice of the minimum value as the norm. The length is measured from the outer borders of the head end and the coccyx. The error of this method according to various sources is ± 3-8 days in the first trimester. In the second and third trimester, the error can reach up to two weeks.

When conducting a screening ultrasound examination in the period of 12-13 weeks, the CTE of the fetus is about 58 mm. During the KTR of the fetus increases by 5-7 mm per week, and already the growth rate of the fetus increases and the KTR can change by 2-3 mm per day.

• Table of dependence of the coccygeal-parietal size of the fetus on the gestational age

  KTR, mm		KTR, mm	Pregnancy, week + day	KTR, mm	Pregnancy, week + day
  3	4	26	9 + 6	61	13 + 1
  4	5 + 2	27	10	62	13 + 2
  5	6 + 1	28	10 + 1	63	13 + 2
  6	6 + 3	30	10 + 2	64	13 + 3
  7	6 + 5	31	10 + 3	65	13 + 3
  8	6 + 6	32	10 + 4	66	13 + 4
  9	7	33	10 + 5	67	13 + 4
  10	7 + 2	34	10 + 6	68	13 + 5
  11	7 + 3	36	11	69	13 + 5
  12	7 + 5	38	11 + 1	70	13 + 5
  13	7 + 6	39	11 + 2	71	13 + 6
  14	8 + 1	41	11 + 3	72	13 + 6
  15	8 + 2	42	11 + 4	73	14
  16	8 + 3	44	11 + 5	74	14
  17	8 + 4	46	11 + 6	75	14 + 1
  18	8 + 5	47	12	76	14 + 1
  19	8 + 6	49	12 + 1	77	14 + 2
  20	9	50	12 + 2	78	14 + 3
  21	9 + 1	51	12 + 3	80	14 + 3
  22	9 + 2	53	12 + 4	82	14 + 4
  23	9 + 3	55	12 + 5	84	14 + 5
  24	9 + 4	58	12 + 6	87	14 + 6
  25	9 + 5	59	13	88	15

  KTR, mm	Pregnancy, week + day
  3	4
  4	5 + 2
  5	6 + 1
  6	6 + 3
  7	6 + 5
  8	6 + 6
  9	7
  10	7 + 2
  11	7 + 3
  12	7 + 5
  13	7 + 6
  14	8 + 1
  15	8 + 2
  16	8 + 3
  17	8 + 4
  18	8 + 5
  19	8 + 6
  20	9
  21	9 + 1
  22	9 + 2
  23	9 + 3
  24	9 + 4
  25	9 + 5

  KTR, mm	Pregnancy, week + day
  26	9 + 6
  27	10
  28	10 + 1
  30	10 + 2
  31	10 + 3
  32	10 + 4
  33	10 + 5
  34	10 + 6
  36	11
  38	11 + 1
  39	11 + 2
  41	11 + 3
  42	11 + 4
  44	11 + 5
  46	11 + 6
  47	12
  49	12 + 1
  50	12 + 2
  51	12 + 3
  53	12 + 4
  55	12 + 5
  58	12 + 6
  59	13

  KTR, mm	Pregnancy, week + day
  61	13 + 1
  62	13 + 2
  63	13 + 2
  64	13 + 3
  65	13 + 3
  66	13 + 4
  67	13 + 4
  68	13 + 5
  69	13 + 5
  70	13 + 5
  71	13 + 6
  72	13 + 6
  73	14
  74	14
  75	14 + 1
  76	14 + 1
  77	14 + 2
  78	14 + 3
  80	14 + 3
  82	14 + 4
  84	14 + 5
  87	14 + 6
  88	15

  The coccyx-parietal size of the fetus practically does not depend on the individual characteristics of the pregnant woman (sex, age, nationality). If fluctuations that significantly exceed the norm (more than one week or more than 7-10 mm) are detected when determining this indicator, this may be a sign of a pathological course of pregnancy.
  

  So, an increase in CTE can be caused by a Rh conflict between the mother and the embryo, a subcompensated course of diabetes in a pregnant woman. An increase is also an early sign of the development of a large fetus. This criterion helps to further adjust the tactics of managing such a pregnancy: limiting the unreasonable intake of metabolic drugs and multivitamin complexes.

  Reasons for the decrease in CTE

  This pathology is confirmed by the absence of movement and heartbeat in the fetus. However, this can only be assessed in the embryo if the CTE is greater than 6 mm. If the coccyx-parietal size is more than 6 mm and the heartbeat is not detected, then, based on the situation, either a second ultrasound scan is recommended after 5-7 days, or emergency surgery.

  Late fertilization due to later ovulation

  This is possible, for example, when pregnancy occurs in a short time after the abolition of hormonal contraceptives. To confirm this reason, it is necessary to conduct a control ultrasound in 10-14 days with the determination of KTR for a more accurate determination of the gestational age.

  Maternal hormonal imbalance

  It is most commonly caused by a progesterone deficiency. In the absence of an adequate appointment of replacement therapy, it is possible to terminate the pregnancy in the early stages. For diagnosis, laboratory methods for determining the level of hormones are used.

  Infectious diseases in the mother

  This is especially true for infections of the urogenital tract (chlamydial, mycoplasma infections). In this regard, it is necessary to conduct a survey for sexually transmitted infections in pregnant women, as well as conduct the necessary antibiotic therapy within an acceptable time frame.

  Genetic diseases

  For example, Shereshevsky-Turner, Patau. If this pathology is suspected, it is necessary to conduct a biochemical examination of pregnant women. If changes are detected in the results of ultrasound and biochemical tests, amniocentesis (collection of amniotic fluid during puncture for further research) or cordocentesis (cord blood sampling) is recommended. However, due to the invasiveness of the method, the consent of the pregnant woman is required to conduct this study.

  Pathology of the uterus

  In particular, changes due to previous abortions and miscarriages. This reason is indicated by the data of the anamnesis and previous ultrasound.

  The development of multiple pregnancy. With such a pathology, it is also possible that the obtained CTE values ​​do not correspond to the data from the table, but this is not a pathology.

  Even severe pathology from the internal organs in the early stages of pregnancy does not affect the development of the fetus. Therefore, the CTE of the fetus does not change during such a pregnancy.

  The scope of the examination required when detecting a deviation of the CTE from the norm is individual in each case and is determined not only by ultrasound data, but also by anamnesis data, clinical data.

  Determination of the hormonal background, examination for the presence of sexually transmitted infections, exclusion of chromosomal diseases. While the examination is being carried out, it is necessary to conduct an ultrasound examination in dynamics, but it is not advisable to conduct it more often than after 5 days.

  In addition to determining the coccygeal-parietal size, during the screening ultrasound, other important indicators are determined:

  1. The presence of a heartbeat and their frequency.
  2. (as an indirect marker of Down syndrome, estimated up to 13 weeks).
  3. The yolk sac, its presence, thickness (determined up to 12 weeks, important in the diagnosis of non-developing pregnancy).
  4. Chorion, its location and structure (information about the location of the placenta in the future, the presence of intrauterine infection and Rh conflict).

  The norms of all these indicators also depend on the period and have established tabular values.

  Conducting a study on high devices and by specialists who have undergone special training allows you to get a reliable conclusion, on which further tactics of pregnancy management are based. They also decide how many and at what time additional ultrasound examinations should be performed if a pathological course of pregnancy is suspected.

What is SVD during pregnancy and how to determine it on ultrasound? There is only one answer to this question.

SVD is the average internal diameter of the fetal egg according to ultrasound diagnostics. This indicator is measured exclusively in millimeters.

gestational sac illustration

The gestational age is characterized by certain values ​​of the inner diameter. The digital value of SVD is constantly changing, so the period is considered with an error of from a week to one and a half. A more reliable sign for clarifying the gestational age by ultrasound is the KTP (coccygeal-parietal size) indicators. It should be noted that the coccyx-parietal size of the embryo is less subject to individual fluctuations compared to the average inner diameter of the fetal egg, and therefore is used more often to establish a reliable gestation period. The error is about three days.

When the fetus is well visualized, the term is determined by the length of the fetus, and not by the internal diameter. The coccygeal-parietal size is fixed during a planned ultrasound and reflects the true size of the fetus in combination with the approximate weight of the fetus. As a rule, the measurement of CTE indicators is used up to 12 weeks of gestation, and in later ultrasound studies, the biparietal diameter of the circumference of the head and abdomen of the fetus is used.

Approximate indicators of SVD, depending on the timing of gestation

• When the diameter of the fetal egg is approximately 4 millimeters, then the gestational age is no more than 5 weeks. It is possible to assume that about four weeks have passed since the day of conception.
• Closer to the fifth week, the diameter will reach 6 millimeters.
• A few days later, the fetus becomes 7 millimeters.
• By the end of the 6th week, the diameter increases to 12 - 18 millimeters.
• The average value of SVD for a period of six weeks and five days is 16 millimeters.

fertilized egg on ultrasound

Of course, the expectant mother is concerned about the following question: how intensively does the fetus grow in the second and third trimester? We can say with confidence that up to 15 - 16 weeks, its diameter grows by one millimeter daily. Then its value increases by an average of 2 - 2.5 millimeters every day. In the border period of 16-17 weeks, they stop measuring the inner diameter of the fetal egg, focusing on more reliable indicators.

Ultrasound examination at a short gestation period

Diagnostics is carried out for the following purposes:

Diagnosis of the localization of the fetal egg

1. Establishing the exact localization of the fetus (in the uterine cavity or outside it). When the fetus is located outside the uterus, we are talking about ectopic pregnancy. When the fetus cannot be visualized or the recognition process is significantly more difficult, then they resort to an accurate determination of the heartbeat of the embryo. Signs of fetal viability may be found in the fallopian tubes or abdominal cavity.

In addition to this complication, other complications may appear at the initial stages of pregnancy: for example, an altered shape of the fetal egg; improper attachment; high risk of placental abruption and other pathological disorders.

2. The definition of a single or multiple pregnancy is not difficult. In the uterine cavity there are two or more fetuses with active vital activity.

3. Evaluation of the main dimensions of the fetal egg and embryo and comparing them with normal indicators.

4. The study of the correct structure of the embryo and fetal egg to exclude serious congenital developmental anomalies. These can be chromosomal mutations (for example, Down syndrome).

5. Assessment of vital signs is carried out on the basis of the presence of a heartbeat, which is detected as early as the fifth week of gestation. The motor activity of the embryo is quite well determined already after the seventh week of gestation.

At the initial stage, the movements are so weak and isolated that they can hardly be distinguished during ultrasound. As the embryo grows, motor activity begins to resemble characteristic flexion and extension movements, and then active movements of the upper and lower limbs. Since individual moments of motor activity are rather short in time and are calculated in seconds or fractions thereof, the definition of cardiac activity is used to register the fact of the fetus's vital activity.

6. Detection in one of the ovaries of the corpus luteum. This small cystic formation provides the body of the expectant mother with important hormones to maintain the fetus in the early stages of development.

7. The study of amnion and chorion is reduced to their ratio depending on the gestation period already in the first trimester. Based on the results of ultrasound, it is possible to predict the further course and outcome of pregnancy.

Ultrasound is indispensable for determining possible problems with pregnancy

8. Diagnosis of threatened miscarriage by ultrasound allows you to recognize early symptoms, which are characterized by a clear thickening of one of the walls of the uterine cavity, as well as a significant increase in the internal pharynx. According to ultrasound, with a possible miscarriage, the vital signs of the fetus and the condition of the uterus and placenta as a whole are assessed.

9. Diagnosis of diseases and possible malformations of the female genital area (malformations of the vagina or uterus). Any deviation from the norm determines the course and outcome of pregnancy.

Typical signs and features of implantation of the fetal egg

Often, the fetal egg is attached to the wall of the uterus after several days after unprotected intercourse, and then the egg is introduced after fertilization into the endometrial layer. From this moment, the hormone hCG (chorionic gonadotropin) begins to be actively produced in the woman's body, to which the pregnancy test strip reacts.

Implantation of the ovum

Not always a screening test will be positive, so it is necessary to resort to a reliable blood test to determine hCG. After receiving a positive test result, it is necessary to contact the gynecologist at the antenatal clinic as soon as possible for registration and further observation for nine months.

The formed fetal egg is the surest sign of the onset of pregnancy. It has a characteristic oval shape and is quite well visualized on ultrasound in the third week of the absence of menstruation.

The embryo itself can be seen only when the period reaches the fifth week. If the ultrasound doctor does not find the embryo in the fetal egg, then the study is repeated after about half a month. As a rule, the embryo becomes more clearly visible, and its heartbeat is also determined. In other cases, we are talking about pathological development or even about a frozen and non-developing pregnancy.

That is why it is very important to undergo an ultrasound scan to exclude possible complications in order to further correct the situation. The first trimester is the most important period of gestation, since throughout it there is an active laying of all organs and systems of the unborn baby.

Scheduled ultrasound diagnostics

According to the results of WHO, strict periods have been determined for mandatory ultrasound examinations during the gestation period of the unborn baby.

Three ultrasound screenings are required

At other time intervals, the behavior of the examination is prescribed strictly according to individual indications from the mother and fetus:

• the first ultrasound examination is recommended at 12-14 weeks;
• the second screening is prescribed for 20 - 24 weeks;
• the third time to visit the ultrasound is necessary at 32 - 34 weeks of gestation.

It is undesirable to neglect the term of the next examination, since it is during the indicated period of gestation that it is possible to recognize malformations of the fetus. And if there is a compelled need - interruption for medical reasons. The last screening examination may be carried out at a later time.

The results of the current diagnostics can be significantly out of the normal range, but this is far from a cause for concern. Do not forget that the development of each child has its own characteristics. However, the identified symptoms should not be ignored either.

What is SVD during pregnancy and how to determine it on ultrasound? There is only one answer to this question.

SVD is the average internal diameter of the fetal egg according to ultrasound diagnostics. This indicator is measured exclusively in millimeters.

gestational sac illustration

The gestational age is characterized by certain values ​​of the inner diameter. The digital value of SVD is constantly changing, so the period is considered with an error of from a week to one and a half. A more reliable sign for clarifying the gestational age by ultrasound is the KTP (coccygeal-parietal size) indicators. It should be noted that the coccyx-parietal size of the embryo is less subject to individual fluctuations compared to the average inner diameter of the fetal egg, and therefore is used more often to establish a reliable gestation period. The error is about three days.

When the fetus is well visualized, the term is determined by the length of the fetus, and not by the internal diameter. The coccygeal-parietal size is fixed during a planned ultrasound and reflects the true size of the fetus in combination with the approximate weight of the fetus. As a rule, the measurement of CTE indicators is used up to 12 weeks of gestation, and in later ultrasound studies, the biparietal diameter of the circumference of the head and abdomen of the fetus is used.

Approximate indicators of SVD, depending on the timing of gestation

• When the diameter of the fetal egg is approximately 4 millimeters, then the gestational age is no more than 5 weeks. It is possible to assume that about four weeks have passed since the day of conception.
• Closer to the fifth week, the diameter will reach 6 millimeters.
• A few days later, the fetus becomes 7 millimeters.
• By the end of the 6th week, the diameter increases to 12 - 18 millimeters.
• The average value of SVD for a period of six weeks and five days is 16 millimeters.

fertilized egg on ultrasound

Of course, the expectant mother is concerned about the following question: how intensively does the fetus grow in the second and third trimester? We can say with confidence that up to 15 - 16 weeks, its diameter grows by one millimeter daily. Then its value increases by an average of 2 - 2.5 millimeters every day. In the border period of 16-17 weeks, they stop measuring the inner diameter of the fetal egg, focusing on more reliable indicators.

Ultrasound examination at a short gestation period

Diagnostics is carried out for the following purposes:

Diagnosis of the localization of the fetal egg

1. Establishing the exact localization of the fetus (in the uterine cavity or outside it). When the fetus is located outside the uterus, we are talking about ectopic pregnancy. When the fetus cannot be visualized or the recognition process is significantly more difficult, then they resort to an accurate determination of the heartbeat of the embryo. Signs of fetal viability may be found in the fallopian tubes or abdominal cavity.

In addition to this complication, other complications may appear at the initial stages of pregnancy: for example, an altered shape of the fetal egg; improper attachment; high risk of placental abruption and other pathological disorders.

2. The definition of a single or multiple pregnancy is not difficult. In the uterine cavity there are two or more fetuses with active vital activity.

3. Evaluation of the main dimensions of the fetal egg and embryo and comparing them with normal indicators.

4. The study of the correct structure of the embryo and fetal egg to exclude serious congenital developmental anomalies. These can be chromosomal mutations (for example, Down syndrome).

5. Assessment of vital signs is carried out on the basis of the presence of a heartbeat, which is detected as early as the fifth week of gestation. The motor activity of the embryo is quite well determined already after the seventh week of gestation.

At the initial stage, the movements are so weak and isolated that they can hardly be distinguished during ultrasound. As the embryo grows, motor activity begins to resemble characteristic flexion and extension movements, and then active movements of the upper and lower limbs. Since individual moments of motor activity are rather short in time and are calculated in seconds or fractions thereof, the definition of cardiac activity is used to register the fact of the fetus's vital activity.

6. Detection in one of the ovaries of the corpus luteum. This small cystic formation provides the body of the expectant mother with important hormones to maintain the fetus in the early stages of development.

7. The study of amnion and chorion is reduced to their ratio depending on the gestation period already in the first trimester. Based on the results of ultrasound, it is possible to predict the further course and outcome of pregnancy.

Ultrasound is indispensable for determining possible problems with pregnancy

8. Diagnosis of threatened miscarriage by ultrasound allows you to recognize early symptoms, which are characterized by a clear thickening of one of the walls of the uterine cavity, as well as a significant increase in the internal pharynx. According to ultrasound, with a possible miscarriage, the vital signs of the fetus and the condition of the uterus and placenta as a whole are assessed.

9. Diagnosis of diseases and possible malformations of the female genital area (malformations of the vagina or uterus). Any deviation from the norm determines the course and outcome of pregnancy.

Typical signs and features of implantation of the fetal egg

Often, the fetal egg is attached to the wall of the uterus after several days after unprotected intercourse, and then the egg is introduced after fertilization into the endometrial layer. From this moment, the hormone hCG (chorionic gonadotropin) begins to be actively produced in the woman's body, to which the pregnancy test strip reacts.

Implantation of the ovum

Not always a screening test will be positive, so it is necessary to resort to a reliable blood test to determine hCG. After receiving a positive test result, it is necessary to contact the gynecologist at the antenatal clinic as soon as possible for registration and further observation for nine months.

The formed fetal egg is the surest sign of the onset of pregnancy. It has a characteristic oval shape and is quite well visualized on ultrasound in the third week of the absence of menstruation.

The embryo itself can be seen only when the period reaches the fifth week. If the ultrasound doctor does not find the embryo in the fetal egg, then the study is repeated after about half a month. As a rule, the embryo becomes more clearly visible, and its heartbeat is also determined. In other cases, we are talking about pathological development or even about a frozen and non-developing pregnancy.

That is why it is very important to undergo an ultrasound scan to exclude possible complications in order to further correct the situation. The first trimester is the most important period of gestation, since throughout it there is an active laying of all organs and systems of the unborn baby.

Scheduled ultrasound diagnostics

According to the results of WHO, strict periods have been determined for mandatory ultrasound examinations during the gestation period of the unborn baby.

Three ultrasound screenings are required

At other time intervals, the behavior of the examination is prescribed strictly according to individual indications from the mother and fetus:

• the first ultrasound examination is recommended at 12-14 weeks;
• the second screening is prescribed for 20 - 24 weeks;
• the third time to visit the ultrasound is necessary at 32 - 34 weeks of gestation.

It is undesirable to neglect the term of the next examination, since it is during the indicated period of gestation that it is possible to recognize malformations of the fetus. And if there is a compelled need - interruption for medical reasons. The last screening examination may be carried out at a later time.

The results of the current diagnostics can be significantly out of the normal range, but this is far from a cause for concern. Do not forget that the development of each child has its own characteristics. However, the identified symptoms should not be ignored either.

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The starting countdown of the origin of human life begins with the fertilization of an egg by a spermatozoon. This fateful meeting takes place in the ampullar part of the fallopian tube, where, in the process of fusion, an embryo appears, consisting of a single cell - the zygote. But even this cell already has a set of 46 chromosomes that is characteristic of a person.

The zygote has two main tasks: to divide actively and to get to the uterine cavity as quickly as possible. An insufficiently active zygote can either die immediately, or, without getting into the uterus, develop as an ectopic pregnancy.

Development of the fetal egg

After 30 hours, the fertilized egg divides into two parts, each of which will also divide in two every day. Cells that are constantly increasing in number and size are called the fetal egg. The fetal egg enters the uterine cavity on the fourth day from the moment of fertilization, and is a collection of only 12 cells. Securely attached to one of the walls of the uterus, the fetal egg continues to divide even more intensively - by the end of the sixth day, there are more than a hundred cells in it.

At first, the fetal egg is a watery substance, which includes the developing embryo and the amniotic fluid surrounding it - a nutrient and protective environment. From the fifth week from the moment of fertilization, the fetal egg is already visualized by ultrasound.

Normally, the fetal egg has a round or oblong shape. A flattened or shapeless appearance may be evidence of genetic abnormalities in the fetus or a sign of uterine tone in a pregnant woman, other pathologies in the course of pregnancy.

The size of the fetal egg is one of the criteria for confirming pregnancy and determining its timing. So, for the first time it is detected on ultrasound no earlier than 5 weeks from the moment of conception, and its size is only 5-6 mm. Modern transvaginal sensors, due to their high resolution, can detect pregnancy even earlier - at a period of 4 weeks, when the size of the fetal egg is only 1 mm.

From the fifth to the tenth week of pregnancy, the size of the fetal egg changes as follows:

• 5 week - 5-6 mm;
• 6 weeks - 11 mm;
• 7 week - 19 mm;
• 8 week - 27 mm;
• 9 week - 35 mm;
• 10 weeks - 44 mm.

The range of time fluctuations can be up to 3 weeks, that is, in one woman, a fetal egg, 20 mm in size, is formed by the end of the sixth week, and in another, only by the beginning of the ninth. Therefore, the size of the fetal egg for gynecologists is not an indisputable and the only reliable indicator of the gestational age. With a minimum error, only pregnancy can be determined in women with a “classic” menstrual cycle of 28 days, who do not have gynecological diseases or other health problems.

Embryo size by week

Approximately at the sixth week, an embryo is determined inside the fetal egg during ultrasound diagnostics. From that moment on, it becomes the main and most reliable source for determining the gestational age.

The length of a 6-week-old embryo fluctuates within 3 mm, but, despite such microscopic dimensions, it is already a full-fledged born life, since you can listen to its heartbeat. The length of the embryo and its heart rate, in contrast to the size of the fetal egg, are less subject to variability. Therefore, the error in determining the gestational age for these indicators is only three days.

Regardless of the size of the ovum, the maximum length of a 6-week-old embryo is 55 mm. Up to 14 weeks, it grows at the following rates:

• 7 week - 8.9 mm;
• 8 week - 14.7 mm;
• 9 week - 21.9 mm;
• 10 week - 30.5 mm;
• 11 weeks - 40.4 mm;
• 12 weeks - 51.7 mm;
• 13 weeks - 64.3 mm;
• 14 weeks - 78.3 mm.

Determining the gestational age and the date of the upcoming birth by the size of the fetal egg and the length of the embryo is advisable only up to 12-14 weeks, that is, in the first trimester. After this time, the embryo moves to the next stage of development - the formation of the fetus. The most reliable data for diagnosing the timing of pregnancy are such data as the circumference of the head and abdomen, physical activity, heart rate, the formation of the circulatory system, limbs.