Shape, structure and dimensions gestational sac weekly allow you to clarify the nature of the course of pregnancy. To determine the values, ultrasound is performed, if the indicators are very different from the norm, additional studies are prescribed to identify possible pathologies.
The fertilized egg helps to understand the nature of the course of pregnancy
Features of the growth and structure of the fetal egg
The amniotic egg is formed at the moment of the fusion of the spermatozoon and the egg, initially consists of the embryo and the membrane, as the fetus grows, the formation structure becomes more complicated, the volume increases.
The main tasks are to provide the embryo with nutrients, support blood circulation on initial stage development, creating the basis for the formation of the placenta, fixing the fetus in the uterine cavity, the synthesis of the hCG hormone.
Stages of formation:
- 7 days after conception, the chorion is formed - the outer dense shell of the embryo, through which oxygen and all useful substances are supplied to the embryo, and protects against infection. As pregnancy progresses, the chorion transforms into the placenta.
- On the surface of the chorion there are many villi, they help the fertilized egg to gain a foothold in the uterus.
- Gradually, the hairs fall off, remain only at the site of attachment of the egg to the uterus, the rest of the surface of the chorion becomes smooth.
- On the 20th day after menstruation, the yolk sac is formed - it performs the functions of the liver, kidneys, spleen, the first germ cells, blood cells, and vessels are formed in it. The absence of such a pouch is a sign of the pathology of pregnancy.
- Inside the shell that surrounds the embryo is the amnion, which produces amniotic fluid.
During a miscarriage, a fertilized egg may fall out
If a miscarriage occurs, a fetal egg comes out, after the termination of pregnancy, a histological examination of tissues is performed, in the presence of chorionic villi, a missed pregnancy is diagnosed. The study allows to exclude cystic drift - a malignant degeneration of cells.
Any ultrasound method is absolutely safe for mother and child. The first months of pregnancy are very important, all organs and systems are formed in the fetus, expectant mothers need to do ultrasound in a timely manner. The study allows you to determine the size of the embryo, accurately determine the gestational age, identify possible pathologies during pregnancy or in the development of the fetus.
Throughout the nine months, every mother worries about the correct development of the baby. It is precisely to ensure full control over the development of the child in the womb and the timely detection of any abnormalities that pregnant women are strongly recommended to regularly visit the leading doctor in order to find out the size of the fetus by weeks of pregnancy.
Accurate diagnosis involves the use of ultrasound methods. Based on the results obtained, the specialist can determine how proportionally the baby develops, and whether the data obtained regarding growth and development correspond to the established norms.
What indicators are taken into account?
The key parameters that make it possible to determine the characteristics of the development of the fetus are indicators of its height and weight, but they begin to be measured only in the second part of the first trimester. Until that time, the dimensions of the embryo are so small that their measurement is extremely difficult.
According to medical indications, every pregnant woman is required to undergo at least three ultrasound examinations during all nine months. This number of procedures is considered minimal and can be increased by the decision of specialists, if there is a need to obtain additional information about the development of the fetus.
Periodic ultrasound is necessary for the timely detection of serious pathologies and the prevention of complications. As a rule, such studies are carried out no earlier than 10 and no later than 14 weeks, as well as in the second trimester in the period from 18 to 21 weeks.
To facilitate the task in medical practice, it is customary to measure the size of the fetus by weeks, because the fetal egg increases in volume almost daily.
The results of each ultrasound are recorded in protocols, from which information can be obtained regarding the symmetry of the development of the fetus, its growth rate and the compliance of indicators with established and used standards.
Throughout pregnancy, as the fetus develops, various parameters are taken into account. For example, up to 13 weeks, experts focus more on the analysis of the coccygeal-parietal length, measured from the coccyx to the parietal region of the fetus. This feature of the measurement is due to the fact that the fetus is in a bent position, so the opportunity to obtain the first data on growth appears no earlier than 14 weeks.
During the second scheduled ultrasound, specialists focus more on other indicators presented:
- fronto-occipital size or longitudinal line;
- circles of the skull, abdomen and chest;
- length of the lower and upper limbs.
An important factor indicating the normal development of the fetus is not only compliance with established standards, but also the symmetry of the measurements obtained.
Fetal size by week of pregnancy
Pregnancy occurs by the end of the second week menstrual cycle, which is considered the moment of conception. The features of this process are known to everyone since school. Male ejaculation is accompanied by the release of millions of spermatozoa, only one of which, after entering the vagina and through the fallopian tubes, will be able to approach the egg.
During the third week, the formation of an embryonic vesicle occurs, inside which there is a large amount of fluid and cells. This bubble is so small that it is almost impossible to see it without special equipment. To be able to imagine the parameters of the bubble, compare it with a pea, the size of which does not exceed 0.2 mm in diameter.
From the beginning of the fourth week, the active development of the fetus begins, which almost doubles every week. So, by the end of the next week, the length of the fetal egg reaches 0.5 mm. Already at this stage, specialists have the first opportunity to obtain real data on the development of the fetus, which can be presented in the form of a table.
Table 1. Dimensions of the ovum from 1 to 13 weeks
|
Period |
Length indicators, mm |
Inner diameter, mm3 |
Area, mm2 | Volume, mm2 | Coccyx-parietal size, mm |
Yolk sac diameter, mm3 |
| 1 Week | — | — | — | — | — | — |
| 2 weeks | — | — | — | — | — | — |
| 3 week | 0,2 | — | — | — | — | — |
| 4 week | 0,5 | — | — | — | — | — |
| 5 week | 1,5 | 18 | 245 | 2 187 | 3 | — |
| 6 week | 4 | 22 | 363 | 3 993 | 6 | 3 |
| 7 week | 7 | 22 | 432 | 6 912 | 10 | 4 |
| 8 week | 10 | 30 | 675 | 13 490 | 16 | 4,5 |
| 9 week | 15 | 33 | 972 | 16 380 | 23 | 5 |
| 10 week | 31 | 39 | 1 210 | 31 870 | 31 | 5,1 |
| 11 week | 55 | 47 | 1 728 | 55 290 | 41 | 5,5 |
| 12 week | 80 | 56 | 2 350 | 87 808 | 53 | 6 |
| 13 week | 105 | 65 | 3 072 | 131 070 | 66 | 6 |
The lengths given in the table are measured from the crown of the head to the coccyx and are averaged. According to experts, due to distinctive features development, slight deviations from the given averages are allowed. A significant deviation, as well as a violation of the permissible proportions between the indicators, which is an important factor, is a prerequisite for further research.
By the end of the eighth week, the length of the fetal egg reaches 11 mm. According to numerous studies, the weight of the fetus at this stage does not exceed 1.5 grams. Over the next week, there is an increase in weight by another 0.5 g, and by the end of the tenth week, it can reach 4 g.
At the eleventh, through ultrasound, it becomes possible to obtain the first data on the length of the thigh and chest, which are respectively 7 and 20 mm. By this period, the weight of the fetus reaches 11 g. By the end of 12 weeks, the diameter of the chest will reach 24 mm, and the diameter of the thigh - 9 mm.
From the 11th to the 40th week, specialists carefully examine not only the general indicators of length, but also the parameters of individual parts of the body, which allows you to get a general and complete picture of the correct development of the fetus.
Starting from the thirteenth, during examinations, measurements of the baby’s skull are also taken into account, whose weight by this time reaches 30 g.
Table 2. Sizes of the fetal egg by week: from the 13th to the 40th
| Period | Length indicators, mm | Thigh length, mm | Chest diameter, mm | Skull perimeter, mm | Skull area, mm2 |
| 11 week | 55 | 7 | 20 | — | — |
| 12 week | 80 | 9 | 24 | — | — |
| 13 week | 105 | 12 | 25 | — | — |
| 14 week | 110 | 16 | 26 | 80 | 510 |
| 15 week | 115 | 19 | 28 | 90 | 675 |
| 16 week | 160 | 22 | 34 | 102 | 860 |
| 17 week | 170 | 24 | 38 | 120 | 1 080 |
| 18 week | 205 | 28 | 41 | 126 | 1 320 |
| 19 week | 215 | 31 | 44 | 138 | 1 450 |
| 20 week | 250 | 34 | 48 | 144 | 1 730 |
| 21 weeks | 260 | 37 | 50 | 151 | 1 875 |
| 22 week | 270 | 40 | 53 | 162 | 2 190 |
| 23 week | 385 | 43 | 56 | 173 | 2 520 |
| 24 week | 300 | 46 | 59 | 183 | 2 710 |
| 25 week | 310 | 48 | 62 | 194 | 3 072 |
| 26 week | 325 | 51 | 64 | 199 | 3 260 |
| 27 week | 340 | 53 | 69 | 215 | 3 675 |
| 28 week | 350 | 55 | 73 | 218 | 3 880 |
| 29 week | 365 | 57 | 76 | 225 | 4 170 |
| 30 week | 375 | 59 | 79 | 234 | 4 563 |
| 31 weeks | 385 | 61 | 81 | 240 | 4 810 |
| 32 week | 400 | 63 | 83 | 246 | 5 040 |
| 33 week | 410 | 65 | 85 | 255 | 5 290 |
| 34 week | 420 | 66 | 88 | 264 | 5 547 |
| 35 week | 450 | 67 | 91 | 270 | 5 810 |
| 36 week | 455 | 69 | 94 | 272 | 6 075 |
| 37 week | 480 | 71 | 97 | 276 | 6 348 |
| 38 week | 485 | 71 | 97 | 282 | 6 620 |
| 39 week | 490 | 73 | 99 | 285 | 6 684 |
| 40 week | 500 | 75 | 101 | 290 | 6 768 |
Biparental fetal size by week
Another important indicator that experts take into account in their studies is the biparietal size, represented by the distance between the outer surface of the upper contour and the inner region of the lower contour between the parietal bones.
As in the case of other indicators, minor deviations from the norm are allowed when analyzing the obtained biparietal size. If the established data is exceeded, the specialist must evaluate other parameters, represented by the circumference of the abdomen, the length of the limbs.
The analysis of this indicator is extremely important, because its deviations from the norm in many cases may indicate serious pathologies, represented by hernias, tumors and other volumetric formations, in which the only way out may be termination of pregnancy. The insufficient development of the baby's head or a decrease in its size is also considered undesirable, which may be due to underdevelopment or lack of anatomical structures of the brain. In this case, experts also strongly recommend termination of pregnancy.
Often in the third trimester, reduced indicators of BDP are diagnosed, which, if detected in a timely manner, can be successfully corrected.
As a rule, in this case, a diagnosis of intrauterine growth retardation is made, and the pregnant woman is prescribed treatment. medicines that help improve uteroplacental blood flow and ensure the transport of essential nutrients.
In medical practice, the following average indicators of the biparietal size of the fetus are used:
- 8 week - 6 mm;
- 9 week - 8.5;
- 10 week - 11 mm;
- 11 weeks - 15 mm;
- 12 weeks - 20 mm;
- 13 week - 24 mm;
- 14 weeks - 26 mm;
- 15 week - 32 mm;
- 16 weeks - 35 mm;
- 17 week - 39 mm;
- 18 weeks - 42 mm;
- 19 week - 44 mm;
- 20 week - 47 mm;
- 21 weeks - 51 mm;
- 22 weeks - 54 mm;
- 23 weeks - 58 mm;
- 24 weeks - 61 mm;
- 25 week - 64 mm;
- 26 weeks - 67 mm;
- 27 week - 69 mm;
- 28 weeks - 72 mm;
- 29 week - 75 mm;
- 30 week - 78 mm;
- 31 weeks - 80 mm;
- 32 weeks - 82 mm;
- 33 weeks - 84 mm;
- 34 weeks - 86 mm;
- 35 week - 88 mm;
- 36 week - 90 mm;
- 37 week - 91 mm;
- 38 weeks - 92 mm;
- 39 week - 94 mm;
- 40 weeks - 95 mm.
Of course, it is not possible to determine the exact weight of the fetus by means of an ultrasound examination, so experts are guided by other sizes and established norms. For the first time, the weight of the fetus is indicated on the eighth week, from which it becomes possible to obtain the first necessary data.
Table 3. Fetal weight by week
| Period | |
| 8 week | 1 |
| 9 week | 2 |
| 10 week | 4 |
| 11 week | 7 |
| 12 week | 14 |
| 13 week | 23 |
| 14 week | 43 |
| 15 week | 70 |
| 16 week | 100 |
| 17 week | 140 |
| 18 week | 190 |
| 19 week | 240 |
| 20 week | 300 |
| 21 weeks | 360 |
| 22 week | 430 |
| 23 week | 501 |
| 24 week | 600 |
| 25 week | 660 |
| 26 week | 760 |
| 27 week | 875 |
| 28 week | 1005 |
| 29 week | 1153 |
| 30 week | 1319 |
| 31 weeks | 1502 |
| 32 week | 1702 |
| 33 week | 1918 |
| 34 week | 2146 |
| 35 week | 2383 |
| 36 week | 2622 |
| 37 week | 2859 |
| 38 week | 3083 |
| 39 week | 3288 |
| 40 week | 3462 |
As a rule, from the data obtained after an ultrasound examination, it is not easy for many women to understand how large the fetus is at this stage. To facilitate this task, the size of the fetal egg by week can be compared with well-known objects. As already noted, the first indicators of the length of the fetus can be obtained only in the third week, when its diameter is 0.2 mm. It is extremely difficult to examine the fetus at this time, and it can only be compared with a poppy seed.
By the end of the fourth week, the fruit almost doubles in size and now it can be safely compared with sesame seeds in size. By the end of the fifth, the fetal egg acquires dimensions comparable to sunflower seeds.
Do you know which bird is considered the smallest on the planet? These are hummingbirds, whose sizes rarely exceed 5.7 centimeters, and their weight is in the range from 1.6 to 2 g. It is with the egg of this bird that a human fetus can be compared in size in the sixth week of its development. By the end of the seventh, its size is comparable to the parameters of an ordinary bean.
On the eighth fruit, in terms of parameters, it can be compared with an unripe olive, and by the end of the ninth - with a large grape.
At the tenth week, the fetus reaches the size of a candy, which doctors do not recommend for pregnant women to lean on. The fruit reaches the size of an apricot by the end of the next period, used as a unit of measurement. At the 12th week, the fruit can be compared with a pea pod, and by the end of the thirteenth - with a ripe fig.
Over the next 7 days, the fruit will grow to the size of a medium pear, and after another week - to the size of an avocado. The average weight of newborn kittens is about 100 g. This is how much a human fetus weighs at the 16th week of its development, and in length it can be compared with an average carrot.
At week 17, the fruit can be compared with a medium potato, and at the end of the eighteenth, with a large tomato.
Imagine a big banana in your hands. It is these sizes that the baby reaches by the end of the nineteenth period. At the 20th week, it can be compared to a small hare. Have you seen such exotic fruit like thai mango? At 21 weeks, the weight of the fetus can be compared with it.
Among the penguins, the largest and heaviest are representatives of the Imperial species, whose height often reaches 125 cm, and their weight is 50 kg. Eggs of emperor penguins weigh up to 450 g. This is how much a human fetus weighs at 22 weeks of its development.
At week 23, it can be compared in terms of length to a corncob, and by the end of week 24, it can be compared to the weight of a green coconut. By the end of the next period, the size of the baby in the womb can be compared with newborn polar bear cubs, which, despite the impressive volume of adults, are born quite small.
By the end of the 26th week, the baby's weight can be compared with an average head of broccoli, and by the 27th - with a pomelo fruit.
If we take for comparison the length of the baby from the heels to the crown, then at 28 weeks it is comparable to the growth of a newborn tiger cub. The largest bird on the planet is the African ostrich, which can grow up to 200 centimeters and weigh 120 kg. The eggs of these birds weigh an average of 1,200 g. It is this weight that is considered the norm for a baby at the 29th week of its development.
By the end of the next period, the child is comparable to the weight of a six-month-old kitten, and by the end of 31 weeks - to the weight of a newborn lion cub.
In terms of growth, a baby at 32 weeks can be compared with a small blue penguin, and by the end of the next period, it reaches the weight of an average pineapple. At week 34, the baby acquires the size of a ripe melon of medium parameters.
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Conception occurs by the fusion of a male sperm with a female egg. As a result of such a connection, an embryo is formed, a group of cells in the shell, which, as they move towards the uterus, begin to divide. After 7 days, it is attached to the uterus, its growth and development begins. The size of the fetal egg by week of pregnancy is determined using ultrasound, 7-10 days after the delay of the monthly cycle.
Formation and emergence of the fetus
The formation of an embryo is based on active division into cellular level. The cells of the embryo grow, due to which the sizes increase. The process continues for 6-7 days, as you move along fallopian tube to the uterine cavity where implantation will occur.Initially, nutrition occurs through independent resources. Once attached, nutrients enter through the uterus, and at the same time, the placenta begins to form to further protect and breathe the baby.
At 4-5 weeks, with the help of ultrasound, you can see a rounded shape, which reaches about 4 mm in diameter. And only at the beginning of the second month of intrauterine development, on the ultrasound monitor, the formed baby becomes noticeable.
Due to various anomalies, the absence of an embryo can be diagnosed when the embryo, for various reasons, has not formed. After a certain period of time, a second study is scheduled to confirm the diagnosis of the heartbeat, which occurs in the middle of the second month.
The fetometric indicator of SVD estimates the diameter and may vary, when determining the gestation period within 10 days. Therefore, in order to determine the term, additional parameters must be taken into account.
The size of the fetal egg by week of pregnancy: table
The size of the ovum at the 5th week of gestation is about 5-6 mm. As the shell grows and develops, the cells continue to actively divide. Already from the 12th week of gestation, the embryo is considered a full-fledged fetus, a child.The gestational age by the size of the shell is determined in accordance with the diameter, area, volume, and is also measured:
- KTP - coccygeal-parietal measurement;
- Biparietal;
- Yolk sac diameter.
| Period by last menstrual period (weeks) | Conception time (weeks) | KTP (coccygeal-parietal size) mm | BR (Bipareital size) mm. | Yolk sac diameter (mm3) |
|---|---|---|---|---|
| Table 1 - The gestational age for the fetal egg | ||||
| 5 | 3 | 18 | 245 | 2187 |
| 6 | 4 | 22 | 363 | 3993 |
| 7 | 5 | 24 | 432 | 6912 |
| 8 | 6 | 30 | 675 | 13490 |
| 9 | 7 | 33 | 972 | 16380 |
| 10 | 8 | 39 | 1210 | 31870 |
| 11 | 9 | 47 | 1728 | 55290 |
| 12 | 10 | 56 | 2350 | 87808 |
| 13 | 11 | 65 | 3072 | 131070 |
| Table 2 - Measurements depending on the period of intrauterine development | ||||
| 5 | 3 | 3 | - | - |
| 6 | 4 | 6 | - | 3 |
| 7 | 5 | 10 | - | 4 |
| 8 | 6 | 16 | 6,0 | 4,5 |
| 9 | 7 | 23 | 8,5 | 5,0 |
| 1 | 8 | 31 | 11,0 | 5,1 |
| 11 | 9 | 41 | 15,0 | 5,5 |
| 12 | 10 | 53 | 20,0 | 6,0 |
| 13 | 11 | 66 | 24,0 | 5,8 |
With a detailed study of the table, it becomes clear that development occurs quite quickly, and assessment is assigned only in the first trimester. After this period, the parameters of the fetus itself will be studied, in which the limbs, head and internal organs will be formed.
Does a fertilized egg grow during a frozen pregnancy?
The shell of the fetus during a missed pregnancy can grow and increase if the formation of an embryo does not occur during cell division, i.e. an empty fetal egg is diagnosed. The pathology is characterized by all the signs of the onset of gestation, hCG is produced and the placenta is formed.This situation is anomalous and occurs quite rarely. It is necessary to determine the absence of an embryo in a timely manner and monitor the growth dynamics so that the body itself stops the formation through a miscarriage. In rare cases, the intervention of specialists for a planned interruption may be required to avoid complications.
The main reasons for stopping development are:
- chronic infectious diseases;
- hereditary factor;
- intoxication medicines;
- unfavorable environment;
- bad habits- Smoking and alcohol abuse.
Only doctors and medical specialists are able to assess the condition of the fetus. It is not necessary to independently determine deviations from the standards, perhaps such a formation will be considered within the normal state.
The period of embryogenesis, that is, when the formation and development of the embryo occurs, lasts from the first to 11-12 weeks of pregnancy. After this period, the embryo is already called a fetus. In this case, the first day of the last menstruation is taken as the starting point.
The development of a new life begins from the moment when the female egg occurs. When the sperm and egg merge, a zygote is formed, which after 26-30 hours begins to divide and forms a multicellular embryo, the size of which, as they say, increases by leaps and bounds.
If in the first four days of its existence the embryo has a size of approximately 0.14 mm, then by the sixth day it reaches 0.2 mm, and by the end of the seventh - 0.3 mm.
On the 7-8th day, the embryo is implanted in the wall of the uterus.
On the 12th day of development, the size of the embryo is already 2 mm.
Change in embryo size by week of pregnancy
- at the 3rd week of embryo development, that is, at the 5th week of pregnancy, the ectoderm forms a groove in the place of the baby's future spine. Then its edges close and a neural tube is formed - the future spinal cord and brain. By the end of this week, the embryo reaches 4 mm;
- in the fourth week, the basis of the central nervous system- spinal cord and brain. The heart makes its first contraction. The rudiments of legs, arms, eyes and internal organs appear, blood begins to flow through the blood vessels;
- at 5-6 weeks, the formation of the head and facial features of the embryo occurs. Its length is about 1 cm
- at week 7, the limbs lengthen and the lungs begin to form. Fully formed heart. Embryo size - 1.5 cm;
- at 8 weeks, all vital organs are almost formed. about 2 cm;
- at 9 weeks, ears, nose, eyelids, mouth, eyes are clearly visible. The growth of the baby is about 3 cm and he continues to grow rapidly;
- at 10 weeks, that is, at 12 weeks of pregnancy, the structure of the skeleton fully corresponds to a person. The limbs are elongated. The blood of the child acquires its own group. The size of the embryo, which is now moving into the status of a fetus, can reach 7 cm.
The increase in the size of the embryo can be seen in the table below.
