Deadline for fetometry. Ultrasound norms by week
For many women during pregnancy, the question of the internal growth and development of the child is very important. Only ultrasound examination can provide such data in the early stages. The size of the fetus is calculated in conjunction with other measurements, since the fetus is in a position that is comfortable for it with its legs tucked in.
There are average standards for the size of a child on ultrasound, but it is worth knowing that this is individual and depends on many factors, including the genetics of the parents.
Fetal size by week of pregnancy
3 weeks.
At the initial stage of pregnancy, the embryo is a small germinal vesicle. On ultrasound, its diameter is about 0.2 mm.
4 weeks.
The size of the embryo reaches 0.5 mm in diameter.
5 weeks.
The length of the embryo is from 1 to 1.5 mm. The ovum has an internal diameter of 18 mm.
The coccygeal-parietal size (CTR) is 3 mm.
6 weeks.
The length of the embryo is about 4 mm. The internal diameter of the ovum is 22 mm.
CTE reaches 6 mm.
PHOTO: 6th week of pregnancy: fetal size according to ultrasound
7 weeks.
The length increases to 1.5 cm. The embryo has a disproportionately large head. The internal diameter of the ovum is 24 mm.
CTE is 10 mm.
PHOTO: 7th week of pregnancy: fetal size according to ultrasound
8 weeks.
It is from this time that ultrasound includes indicators of fetal weight, which at 8 weeks is from 1 to 1.5 g.
The length of the embryo from the coccyx to the parietal region can reach 2.2 cm. It is the measurement of the parietal-coccygeal length that continues throughout pregnancy, since even after the fetus is fully formed, it is impossible to measure it from the crown to the heels (the natural position of the embryo is bent legs).
The average internal diameter of an egg is 30 mm.
CTE is 16 mm.
Biparental head size (BSD) – 6 mm.
PHOTO: 8th week of pregnancy: fetal size according to ultrasound
9 weeks.
Weight approximately 2 g. Length from the parietal region to the sacrum from 13 to 17 cm.
The fertilized egg has an internal diameter of 33 mm.
KTR – 23 mm.
BPR – 8.5 mm.
PHOTO: 9th week of pregnancy: fetal size according to ultrasound
Week 10
Weight no more than 4 g.
The distance from the crown to the lower back is from 27 to 35 mm.
The average size of the internal diameter of the ovum is 39 mm.
KTR – 31 mm.
BPR - 11 mm.
PHOTO: 10th week of pregnancy: fetal size according to ultrasound
11 weeks.
The length of the fetus from the crown to the sacrum is about 55 mm. Weight reaches 7 g.
The internal diameter of the ovum is 47 mm.
KTR – 41 mm.
BPR – 15 mm.
From the 11th week, the approximate height and weight of the fetus is calculated using ultrasound. This requires measurements of thigh length and diameter chest.
Fruit dimensions:
Fetal height – 6.8 cm.
Thigh length – 6.5 mm.
The chest has a diameter of 20 mm.
PHOTO: 11th week of pregnancy: fetal size according to ultrasound
12 weeks.
The length of the fetus from the crown to the sacrum is from 70 to 90 mm.
Weight reaches 14-15 g.
The average internal diameter of the ovum is 56 mm.
KTR – 53 mm.
BPR – 20 mm.
Fruit dimensions:
Fetal height – 8.2 cm.
Thigh length – 9 mm.
PHOTO: 12th week of pregnancy: fetal size according to ultrasound
13 weeks.
The length of the fetus from the crown to the sacral region is 10 cm. Weight reaches 25 g.
The average internal diameter of the ovum is 65 mm.
KTR – 65 mm.
BPR – 24 mm.
Fruit dimensions:
Fetal height – 10 cm.
Thigh length – 12 mm.
The chest has a diameter of 24 mm.
PHOTO: 13th week of pregnancy: fetal size according to ultrasound
14 weeks.
The length of the fetus from the crown to the sacrum is 11 cm. Weight can reach 43 g.
Baby head dimensions:
BPR – 26 mm.
The perimeter of the skull is 80 mm.
Skull area - 510 mm2.
Fruit dimensions:
Fetal height – 12 cm.
Thigh length – 16 mm.
The chest diameter is 26 mm.
PHOTO: 14th week of pregnancy: fetal size according to ultrasound
15 weeks.
The length of the fetus from the crown to the sacrum is 11 cm. Weight can reach 70 g.
Baby head dimensions:
BPR – 32 mm.
The perimeter of the skull is 90 mm.
Skull area - 675 mm2.
Fruit dimensions:
Fetal height – 14.2 cm.
Thigh length – 19 mm.
The chest has a diameter of 28 mm.
PHOTO: 15th week of pregnancy: fetal size according to ultrasound
16 weeks.
The length of the fetus from the crown to the sacral region is 16 cm. Weight can reach 85 g.
Baby head dimensions:
BPR – 35 mm.
The perimeter of the skull is 102 mm.
Skull area - 860 mm2.
Fruit dimensions:
Fetal height – 16.2 cm.
Thigh length – 22 mm.
The chest has a diameter of 34 mm.
PHOTO: 16th week of pregnancy: fetal size according to ultrasound
17 weeks.
The length of the fetus from the crown to the sacral region is 17 cm. Weight is approximately 142 g.
Baby head dimensions:
BPR – 39 mm.
The perimeter of the skull is 120 mm.
Skull area - 1080 mm2.
Fruit dimensions:
Fetal height – 18 cm.
Thigh length – 24 mm.
The chest has a diameter of 38 mm.
PHOTO: 17th week of pregnancy: fetal size according to ultrasound
18 weeks.
The length of the fetus from the crown to the sacral region is 20 cm. Weight can reach 200 g.
Baby head dimensions:
BPR – 42 mm.
The perimeter of the skull is 126 mm.
Skull area - 1320 mm2.
Fruit dimensions:
Fetal height – 20 cm.
Thigh length – 28 mm.
The chest has a diameter of 41 mm.
PHOTO: 18th week of pregnancy: fetal size according to ultrasound
19 weeks.
The length of the fetus from the crown to the sacrum is 20-22 cm. Weight can reach 230 g.
Baby head dimensions:
BPR – 44 mm.
The perimeter of the skull is 138 mm.
Skull area - 1450 mm2.
Fruit dimensions:
Fetal height – 22 cm.
Thigh length – 31 mm.
The chest has a diameter of 44 mm.
PHOTO: 19th week of pregnancy: fetal size according to ultrasound
20 weeks.
The length of the fetus from the crown to the sacral region is 25 cm. Weight can reach 280 g.
Baby head dimensions:
BPR – 47 mm.
The perimeter of the skull is 144 mm.
Skull area - 1730 mm2.
Fruit dimensions:
Fetal height – 24 cm.
Thigh length – 34 mm.
The chest diameter is 48 mm.
PHOTO: 20th week of pregnancy: fetal size according to ultrasound
21 weeks.
The length of the fetus from the crown to the sacral region is 25 cm. Weight is from 360 to 370 g.
Baby head dimensions:
BPR – 51 mm.
The perimeter of the skull is 151 mm.
The area of the skull is 1870 mm2.
Fruit dimensions:
Fetal height – 26 cm.
Thigh length – 37 mm.
The chest has a diameter of 50 mm.
PHOTO: 21 weeks of pregnancy: fetal size according to ultrasound
22 weeks.
The length of the fetus from the crown to the sacral region is 27 cm. Weight is from 425 to 430 g.
Baby head dimensions:
BPR – 54 mm.
The perimeter of the skull is 162 mm.
Skull area - 2190 mm2.
Fruit dimensions:
Fetal height – 28 cm.
Thigh length – 40 mm.
The chest diameter is 53 mm.
PHOTO: 22 week of pregnancy: fetal size according to ultrasound
23 weeks.
The length of the fetus from the crown to the sacral region is 30 cm. Weight is 500 g.
Baby head dimensions:
BPR – 58 mm.
The perimeter of the skull is 170 mm.
Skull area - 2520 mm2.
Fruit dimensions:
Fetal height – 30 cm.
Thigh length – 43 mm.
The chest diameter is 56 mm.
PHOTO: 23rd week of pregnancy: fetal size according to ultrasound
24 weeks.
The length of the fetus from the crown to the sacral region is 30 cm. Weight is 590 g.
Baby head dimensions:
BPR – 61 mm.
The perimeter of the skull is 183 mm.
Skull area - 2710 mm2.
Fruit dimensions:
Fetal height – 31 cm.
Thigh length – 46 mm.
The chest diameter is 59 mm.
PHOTO: 24th week of pregnancy: fetal size according to ultrasound
25 weeks.
The length of the fetus from the crown to the sacrum is approximately 31 cm.
Weight from 700 g.
Baby head dimensions:
BPR – 64 mm.
The perimeter of the skull is 194 mm.
Skull area -3072 mm2.
Fruit dimensions:
Fetal height – 32 cm.
Thigh length – 48 mm.
The chest diameter is 62 mm.
PHOTO: 25th week of pregnancy: fetal size according to ultrasound
26 weeks.
The length of the fetus from the crown to the sacral region is approximately 32-33 cm. Weight - 800 g.
Baby head dimensions:
BPR – 67 mm.
The perimeter of the skull is 199 mm.
Skull area - 3260 mm2.
Fruit dimensions:
Fetal height – 33 cm.
Thigh length – 51 mm.
The chest diameter is 64 mm.
PHOTO: 26th week of pregnancy: fetal size according to ultrasound
27 weeks.
The length of the fetus from the crown to the sacrum is approximately 34 cm. Weight is 900 g.
Baby head dimensions:
BPR – 68 mm.
The perimeter of the skull is 215 mm.
Skull area - 3675 mm2.
Fruit dimensions:
Fetal height – 35.5 cm.
Thigh length – 53 mm.
The chest diameter is 69 mm.
PHOTO: 27th week of pregnancy: fetal size according to ultrasound
28 weeks.
The length of the fruit from the crown to the sacrum is approximately 35 cm. Weight is 1000 g.
Baby head dimensions:
BPR – 72 mm.
The perimeter of the skull is 218 mm.
Area - 3880 mm2.
Fruit dimensions:
Fetal height – 37 cm.
Thigh length – 55 mm.
The chest diameter is 73 mm.
PHOTO: 28th week of pregnancy: fetal size according to ultrasound
29 weeks.
The length of the fetus from the crown to the sacrum is approximately 37 cm.
Weight - 1150 g.
Baby head dimensions:
BPR – 75 mm.
The perimeter of the skull is 225 mm.
Area - 4100 mm2.
Fruit dimensions:
Fetal height – 39 cm.
Thigh length – 57 mm.
The chest diameter is 76 mm.
PHOTO: 29th week of pregnancy: fetal size according to ultrasound
30 weeks.
The length of the fetus from the crown to the sacrum is approximately 37.5 cm.
Weight can reach 1400 g.
Baby head dimensions:
BPR – 78 mm.
The perimeter of the skull is 234 mm.
Skull area - 4563 mm2.
Fruit dimensions:
Fetal height – 40 cm.
Thigh length – 59 mm.
The chest diameter is 79 mm.
PHOTO: 30th week of pregnancy: fetal size according to ultrasound
31 weeks.
The length of the fetus from the crown to the sacrum is 38-39 cm. Weight can reach 1500 g.
Baby head dimensions:
BPR – 80 mm.
The perimeter of the skull is 240 mm.
Skull area - 4810 mm2.
Fruit dimensions:
Fetal height – 41 cm.
Thigh length – 61 mm.
The chest diameter is 81 mm.
PHOTO: 31 weeks of pregnancy: fetal size according to ultrasound
32 weeks.
The length of the fetus from the crown to the sacrum is approximately 40 cm. Weight is 1700 g.
Baby head dimensions:
BPR – 82 mm.
The perimeter of the skull is 246 mm.
Skull area - 5040 mm2.
Fruit dimensions:
Fetal height – 42 cm.
Thigh length – 63 mm.
The chest diameter is 83 mm.
PHOTO: 32 week of pregnancy: fetal size according to ultrasound
33 weeks.
The length of the fetus from the crown to the sacral region is 42 cm. Weight is 1800 g.
Baby head dimensions:
BPR – 84 mm.
The perimeter of the skull is 255 mm.
Skull area - 5290 mm2.
Fruit dimensions:
Fetal height – 43.5 cm.
Thigh length – 65 mm.
The chest diameter is 85 mm.
PHOTO: 33 week of pregnancy: fetal size according to ultrasound
34 weeks.
The length of the fetus from the crown to the sacral region is 42 cm. Weight is 2000 g.
Baby head dimensions:
BPR – 86 mm.
The perimeter of the skull is 265 mm.
Skull area - 5547 mm2.
Fruit dimensions:
Fetal height is 44.5 cm.
Thigh length – 66 mm.
The chest diameter is 88 mm.
PHOTO: 34th week of pregnancy: fetal size according to ultrasound
35 weeks.
The length of the fetus from the crown to the sacral region is 45 cm. Weight is 2200 g.
Baby head dimensions:
BPR – 88 mm.
The perimeter of the skull is 270 mm.
Skull area - 5810 mm2.
Fruit dimensions:
Fetal height – 45.5 cm.
Thigh length – 67 mm.
The chest diameter is 91 mm.
36 weeks.
The length of the fetus from the crown to the sacral region is 46 cm. Weight is 2300 g.
Baby head dimensions:
BPR – 90 mm.
The perimeter of the skull is 272 mm.
Skull area - 6075 mm2.
Fruit dimensions:
Fetal height – 46.5 cm.
Thigh length – 69 mm.
The chest diameter is 94 mm.
37 weeks.
The length of the fetus from the crown to the sacral region is 48 cm. Weight is 2800 g.
Baby head dimensions:
BPR – 91 mm.
The perimeter of the skull is 276 mm.
Skull area - 6348 mm2.
Fruit dimensions:
Fetal height – 48 cm.
Thigh length – 71 mm.
The chest diameter is 97 mm.
38 weeks.
The length of the fetus from the crown to the sacral region is 50 cm. Weight is 2900 g.
Baby head dimensions:
BPR – 92 mm.
The perimeter of the skull is 282 mm.
Skull area - 6620 mm2.
Fruit dimensions:
Fetal height – 48 cm.
Thigh length – 71 mm.
The chest diameter is 98 mm.
39 weeks.
The length of the fetus from the crown to the sacral region is 50 cm. Weight is 3000 g.
Baby head dimensions:
BPR – 94 mm.
The perimeter of the skull is 285 mm.
Skull area - 6680 mm2.
Fruit dimensions:
Fetal height – 49 cm.
Thigh length – 73 mm.
The chest diameter is 99 mm.
40 weeks.
The length of the fetus from the crown to the sacral region is 51 cm.
Weight - 3000 g.
Baby head dimensions:
BPR – 95 mm.
The perimeter of the skull is 290 mm.
Skull area - 6770 mm2.
Fruit dimensions:
Fetal height – 50 cm.
Thigh length – 75 mm.
The chest diameter is 100 mm.
Do not forget about the error in average values, as well as about the correct gestational age, which can lead to an error in calculating the size of the fetus. In case of multiple pregnancy, other parameters and some lag in size are important.
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From the moment of registration, obstetricians-gynecologists closely monitor the health of the woman and the fetus. Throughout the entire gestation period, the pregnant woman undergoes routine examinations. Some detected problems can be solved medically or surgically, while others require termination of pregnancy. One of the mandatory diagnostic methods, which allows you to find out the parameters of fetal development, is fetometry. How is fetometry done and what indicators are considered normal?
What is fetometry and what are its purposes?
To have an idea of the child’s development (whether it is progressing normally or if there are abnormalities), doctors need to constantly monitor the fetus’s indicators. One of the routine examinations that is prescribed to all women, regardless of the individual characteristics of gestation, is fetometry.
What does fetal fetometry include? This is a determination of the size of the fetus - height and weight. In ultrasound diagnostics, the following indicators are considered key (their abbreviations in Russian and English language and decryption):
- MP, FW – mass;
- KTP, CRL – coccygeal-parietal size;
- BPD, BPD – biparietal size of the embryo's head;
- DB, FL – size of the femur;
- OB, AC – abdominal circumference;
- OG, NS – head circumference;
- LZR, OFD – fronto-occipital size.
Fetometry is carried out using ultrasound. A pregnant woman undergoes sonography as planned in each trimester - at 11–14 (most often 12) weeks, 18–21 weeks and 32–33 weeks. As a rule, sonography is performed in the usual way through the abdominal cavity or transvaginally. No special preparation is required for the examination; only in the first trimester, before a transabdominal examination, a woman needs to drink 1 liter of water 1 hour before visiting the office so that the bladder is full.
It is impossible to draw conclusions about the correct development of the fetus using fetometry alone. The child’s parameters will largely depend on his genetic and individual characteristics. If the mother and father are large, then the baby will be ahead of his peers in development. If growth is delayed, a repeat ultrasound scan is required after 2 weeks; often the baby manages to catch up by this time.
What is assessed at the first ultrasound?
The first screening ultrasound examination is sent soon after the woman is registered. The optimal date for ultrasound diagnostics is 11–12 weeks, but if a pregnant woman comes to the antenatal clinic later, she may be sent for sonography immediately. Why is a screening examination prescribed at these times? One of the most significant indicators in the early stages of gestation is the thickness of the nuchal space of the embryo. Previously, this parameter was indistinguishable, but after the 14th week it fills with lymph, distorting the readings.
Normal indicators
At the first ultrasound, the doctor measures the heart rate of the fetus and looks for the presence of vital organs. Also pay close attention to the following parameters:
- TVP is the area between the soft tissues that cover the spine and the inner surface of the skin. Allows you to detect chromosomal abnormalities, such as Down syndrome.
- KTP – coccygeal-parietal size. It is used to calculate the size of the fetus and gestational age.
The table contains the norms for ultrasound results in the 1st trimester:
What does an embryo look like compared to fruit? Until the first month, it resembles the size of a poppy seed. By the end of the second month, it corresponds to a large grape of 5 cm. During the period of the first fetometric study, it is comparable to a ripe fig of 7 cm.
What is considered a deviation from the norm and why?
To determine the norm and deviations in medical practice, the concept of percentiles is used. Among a large sample, the average value is determined - it is called the 50th percentile. The ultrasound norm is within the 5–95 percentile, and everything that goes beyond this range is regarded as a deviation.
Inconsistency normal values indicates the possibility of intrauterine diseases and developmental anomalies:
- Increased TVP often indicates the presence of genetic pathologies, which include Down syndrome. Its likelihood is indicated by a high TPT, which stands for prenasal tissue thickness. If a discrepancy with the standards is detected, the woman is sent for additional examinations - analysis for alpha-fetoprotein, hCG, amniocentesis, placentocentesis, cordocentesis.
- Irregular heart rhythm may be a consequence of congenital heart disease or hypoxia. Tachycardia and bradycardia may indicate oxygen starvation.
- A high CTE, ahead of the values by 1–2 weeks, is considered normal by doctors. Most often, this indicates that the child will be large. If the mother has diabetes mellitus or the likelihood of developing Rh conflict is increased, then additional examinations are required.
- If deviations in the anatomy of the fetus are detected (incorrect anatomy of the bones of the cranial vault, spine, stomach, heart, limbs, abdominal wall), the sonologist enters them in a special column. Together with an obstetrician-gynecologist and, if necessary, geneticists, a conclusion is made on the advisability of prolonging gestation.
What indicators are studied in the second trimester?
Previously, ultrasound diagnostics in the second trimester were performed at the 25th week of pregnancy, but now they are performed at the 4th month of gestation. This is due to the need to detect malformations at an earlier stage. In addition to the parameters of the fetus, during this period the child's place, its size and degree of maturity are studied.
Standard sizes
In the second trimester of pregnancy, you can better see the size of the baby and specific organs. During this period, more attention is paid to the following ultrasound indicators:
- baby's weight;
- height;
- abdominal circumference;
- fronto-occipital size;
- biparietal head size;
- shin size;
- thigh length;
- humerus size;
- length of the forearm bone.
The table shows the results of fetometry in the 2nd trimester in accordance with the protocol:
| Gestation week | Weight, g | Length, cm | Coolant, mm | OG, mm | LZR, mm | BPR, mm | DG, mm | DB, mm | DP, mm | DCP, mm |
| Week 16 | 100 | 11,6 | 88–116 | 112–136 | 41–49 | 31–37 | 15–21 | 17–23 | 15–21 | 12–18 |
| Week 17 | 140 | 13 | 93–131 | 121–149 | 46–54 | 34–45 | 17–25 | 20–28 | 17–25 | 15–21 |
| Week 18 | 190 | 14,2 | 104–144 | 131–161 | 49–59 | 37–47 | 20–28 | 23–31 | 20–28 | 17–23 |
| Week 19 | 240 | 15,3 | 114–154 | 142–174 | 53–63 | 41–49 | 23–31 | 26–34 | 23–31 | 20–26 |
| Week 20 | 300 | 16,4 | 124–164 | 154–186 | 56–68 | 43–43 | 26–34 | 29–37 | 26–34 | 22–29 |
At the second screening study, it is already possible to assess the size of the placenta. At week 20 it ranges from 1.67–2.86 cm. Amniotic fluid index by week:
- 16 – 74–202;
- 17 – 78–212;
- 18 – 81–221;
- 19 – 84–226;
- 20 – 87–231.
What do deviations from the standard indicate?
Advanced maturation of the placenta is most often observed in mothers who smoke. In addition, this indicator is affected by the presence of diabetes mellitus, the development of gestosis, and the occurrence of intrauterine infections.
Polyhydramnios indicates defects in the development of the child, Rh conflict. Oligohydramnios indicates severe abnormalities in intrauterine development, pathologies, or absence of kidneys in the fetus.
Visualization may be difficult due to the high content of subcutaneous fat. In this case, the doctor indicates in the protocol the cause of the difficulty - PZhK.
The second screening ultrasound allows you to detect pathologies of fetal development that were not visible during the first examination:
- developmental delay if the indicators are symmetrically below the specified norm;
- asymmetrical reduction of the femur, humerus, tibia and forearm indicate skeletal dysplasia;
- an enlarged skull indicates hydrocephalus;
- by measuring the face one can judge the presence of pathologies such as cyclopia, anophthalmia, cleft lip and palate;
- scanning the spine helps to detect spinal bifida;
- the absence, underdevelopment or abnormal structure of internal organs indicates intrauterine anomalies that are incompatible with life.
Fetal fetometry parameters in the third trimester
The third ultrasound of the fetus is prescribed for 32–33 weeks of gestation, although according to individual indications the period can be shifted by several weeks. During this period, the baby is already fully formed, and it becomes possible to evaluate developmental defects that were not visible before. Particular attention is paid to the placenta and amniotic fluid, as well as fetal presentation.
Table of normal sizes of the fetus, body parts and organs
Final fetometry is important, because it is based on its results that doctors choose the method of management. birth process. In the final trimester, the average data on the baby's size and weight are also assessed.
The table shows the average fetometry indicators in the third trimester:
On an ultrasound, the obstetrician-gynecologist looks at the presentation of the fetus, and the delivery tactics depend on this:
- direct cephalic presentation - natural delivery;
- oblique, transverse or direct pelvic presentation - caesarean section (usually).
Possible deviations and their interpretation
Deviations from normal indicators make it possible to predict possible complications during the birth process and detect congenital malformations. Interpretation of deviations:
- Weight and height are greater than normal. A large baby will complicate the delivery process. This may be an indication for surgical intervention, otherwise the woman in labor will experience ruptures as the baby passes through the birth canal.
- Low location of the placenta. In such a situation, natural childbirth is acceptable, but the risk of bleeding is high.
- In the third trimester, abnormalities that were not apparent before become visible. At the last examination, a cleft lip, cleft palate, and aneurysm of the vein of Galen can be detected.
- Indicators below normal allow one to diagnose developmental delay syndrome. This diagnosis allows timely measures to be taken to maintain the baby’s life.
Rules for decoding the ultrasound result by a specialist
Interpretation of ultrasound during pregnancy is performed only by a sonologist, and the diagnosis is made by an obstetrician-gynecologist, who is based on ultrasound diagnostic indicators and other methods. The calculation of indicators is carried out according to obstetric weeks, which are counted from the date of the last menstruation. In fact, the fetus is 1.5–2 weeks younger, but to avoid errors in calculations, gynecologists use a system of counting from the first day of menstruation.
One of the basic rules that guide specialists when interpreting ultrasound is not to make a diagnosis based on sonography results alone. If an abnormal course of gestation is suspected, the pregnant woman is prescribed a re-examination and referred for additional diagnostics.
Despite the fact that the ultrasound report indicates specific numbers - limb length, volume, height and weight, you should not try to interpret them yourself. The limits of normal indicators are large, borderline data does not necessarily indicate deviations, and the expectant mother needs to protect herself from stress.
Throughout the nine months, every mother worries about the correct development of the baby. It is to ensure full control over the development of the child in the womb and timely detection of any abnormalities that pregnant women are strongly recommended to regularly visit a leading doctor in order to find out the size of the fetus by week of pregnancy.
Accurate diagnosis involves the use of ultrasound methods. Based on the results obtained, the specialist can determine how proportionally the baby is developing, and whether the data obtained regarding growth and development correspond to established standards.
What indicators are taken into account?
The key parameters that make it possible to determine the characteristics of fetal development 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 size of the embryo is so small that measuring it is extremely difficult.
According to medical indications, every pregnant woman is required to undergo at least three ultrasound procedures throughout the entire 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 fetal development.
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 from 18 to 21 weeks.
To make the task easier, in medical practice it is customary to measure the size of the fetus by weeks, because the fertilized 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 fetal development, its growth rate and compliance of indicators with established and used standards.
Throughout pregnancy, various parameters are taken into account as the fetus develops. For example, until the 13th week, experts focus more on analyzing the coccygeal-parietal length, measured from the coccyx to the parietal region of the fetus. This measurement feature 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 the 14th week.
During the second planned ultrasound, specialists focus more on other indicators presented:
- fronto-occipital size or longitudinal line;
- circumferences of the skull, abdomen and chest;
- the 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 at the end of the second week of the menstrual cycle, which is considered the moment of conception. The features of this process are known to everyone from school. Male ejaculation is accompanied by the release of millions of sperm, 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 the germinal vesicle occurs, inside which there is fluid and cells in large quantities. This bubble is so small that it is almost impossible to see it without special equipment. To be able to imagine the parameters of a 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, active development of the fetus begins, which almost doubles in size every week. So, by the end of the next week, the length of the fertilized egg reaches 0.5 mm. Already at this stage, specialists have the first opportunity to obtain real data on fetal development, which can be presented in the form of a table.
Table 1. Dimensions of the fertilized egg 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 week | — | — | — | — | — | — |
| 3 week | 0,2 | — | — | — | — | — |
| 4 week | 0,5 | — | — | — | — | — |
| 5 week | 1,5 | 18 | 245 | 2 187 | 3 | — |
| week 6 | 4 | 22 | 363 | 3 993 | 6 | 3 |
| week 7 | 7 | 22 | 432 | 6 912 | 10 | 4 |
| 8 week | 10 | 30 | 675 | 13 490 | 16 | 4,5 |
| Week 9 | 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 |
| Week 13 | 105 | 65 | 3 072 | 131 070 | 66 | 6 |
The lengths given in the table are measured from the crown to the tailbone and are averaged. According to experts, due to the distinctive features of development, minor deviations from the given average indicators are allowed.
A significant deviation, as well as a violation of acceptable proportions between indicators, which is an important factor, is a prerequisite for further research.
On the eleventh, through ultrasound examination, it becomes possible to obtain the first data regarding the length of the thigh and chest, which are 7 and 20 mm, respectively. By this period, the weight of the fetus reaches 11 g. By the end of the 12th week, 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 length indicators, but also the parameters of individual parts of the body, which allows them 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 fertilized egg by week: from 13th to 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 | — | — |
| Week 13 | 105 | 12 | 25 | — | — |
| Week 14 | 110 | 16 | 26 | 80 | 510 |
| Week 15 | 115 | 19 | 28 | 90 | 675 |
| Week 16 | 160 | 22 | 34 | 102 | 860 |
| Week 17 | 170 | 24 | 38 | 120 | 1 080 |
| Week 18 | 205 | 28 | 41 | 126 | 1 320 |
| Week 19 | 215 | 31 | 44 | 138 | 1 450 |
| Week 20 | 250 | 34 | 48 | 144 | 1 730 |
| 21 weeks | 260 | 37 | 50 | 151 | 1 875 |
| Week 22 | 270 | 40 | 53 | 162 | 2 190 |
| Week 23 | 385 | 43 | 56 | 173 | 2 520 |
| Week 24 | 300 | 46 | 59 | 183 | 2 710 |
| Week 25 | 310 | 48 | 62 | 194 | 3 072 |
| Week 26 | 325 | 51 | 64 | 199 | 3 260 |
| Week 27 | 340 | 53 | 69 | 215 | 3 675 |
| Week 28 | 350 | 55 | 73 | 218 | 3 880 |
| Week 29 | 365 | 57 | 76 | 225 | 4 170 |
| Week 30 | 375 | 59 | 79 | 234 | 4 563 |
| 31 weeks | 385 | 61 | 81 | 240 | 4 810 |
| Week 32 | 400 | 63 | 83 | 246 | 5 040 |
| Week 33 | 410 | 65 | 85 | 255 | 5 290 |
| 34 week | 420 | 66 | 88 | 264 | 5 547 |
| Week 35 | 450 | 67 | 91 | 270 | 5 810 |
| Week 36 | 455 | 69 | 94 | 272 | 6 075 |
| Week 37 | 480 | 71 | 97 | 276 | 6 348 |
| Week 38 | 485 | 71 | 97 | 282 | 6 620 |
| Week 39 | 490 | 73 | 99 | 285 | 6 684 |
| Week 40 | 500 | 75 | 101 | 290 | 6 768 |
Biparental fetal size by week
Another important indicator that experts take into account in their research 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 is the case with other indicators, when analyzing the resulting biparietal size, minor deviations from the norm are allowed. If the established data is exceeded, the specialist must evaluate other parameters, represented by abdominal circumference and limb length.
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 space-occupying formations, in which the only way out may be termination of pregnancy. Insufficient development of the baby’s head or a decrease in its size is also considered undesirable, which may be due to underdevelopment or absence of anatomical structures of the brain. In this case, experts also strongly recommend termination of pregnancy.
Often, in the third trimester, reduced indicators of BPD 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, helping to improve uteroplacental blood flow and ensuring the transport of essential nutrients.
In medical practice, the following average indicators of biparietal dimensions of the fetus are used:
- 8 week – 6 mm;
- 9 week – 8.5;
- 10 week – 11 mm;
- 11 week – 15 mm;
- 12 week – 20 mm;
- 13 week – 24 mm;
- 14 week – 26 mm;
- 15 week – 32 mm;
- 16 week – 35 mm;
- 17 week – 39 mm;
- 18 week – 42 mm;
- 19 week – 44 mm;
- 20 week – 47 mm;
- 21 weeks – 51 mm;
- 22 week – 54 mm;
- 23 week – 58 mm;
- 24 week – 61 mm;
- 25 week – 64 mm;
- 26 week – 67 mm;
- 27 week – 69 mm;
- 28 week – 72 mm;
- 29 week – 75 mm;
- 30 week – 78 mm;
- 31 weeks – 80 mm;
- 32 week – 82 mm;
- 33 week – 84 mm;
- 34 week – 86 mm;
- 35 week – 88 mm;
- 36 week – 90 mm;
- 37 week – 91 mm;
- 38 week – 92 mm;
- 39 week – 94 mm;
- 40 week – 95 mm.
Of course, it is not possible to establish through ultrasound examination exact weight fetus, so experts focus on other sizes and established standards. For the first time, the weight of the fetus is indicated in the eighth week, from which it becomes possible to obtain the first necessary data.
Table 3. Fetal weight by week
| Period | |
| 8 week | 1 |
| Week 9 | 2 |
| 10 week | 4 |
| 11 week | 7 |
| 12 week | 14 |
| Week 13 | 23 |
| Week 14 | 43 |
| Week 15 | 70 |
| Week 16 | 100 |
| Week 17 | 140 |
| Week 18 | 190 |
| Week 19 | 240 |
| Week 20 | 300 |
| 21 weeks | 360 |
| Week 22 | 430 |
| Week 23 | 501 |
| Week 24 | 600 |
| Week 25 | 660 |
| Week 26 | 760 |
| Week 27 | 875 |
| Week 28 | 1005 |
| Week 29 | 1153 |
| Week 30 | 1319 |
| 31 weeks | 1502 |
| Week 32 | 1702 |
| Week 33 | 1918 |
| 34 week | 2146 |
| Week 35 | 2383 |
| Week 36 | 2622 |
| Week 37 | 2859 |
| Week 38 | 3083 |
| Week 39 | 3288 |
| Week 40 | 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 fertilized egg by week can be compared with well-known objects. As already noted, the first indicators of fetal length can be obtained only in the third week, when its diameter is 0.2 mm. It is extremely difficult to examine the fruit at this stage, and it can only be compared with a poppy seed.
By the end of the fourth week, the fruit almost doubles in size and can now be compared in size to sesame seeds. By the end of the fifth period, the fertilized egg acquires dimensions comparable to sunflower seeds.
Do you know which bird is considered the smallest on the planet? These are hummingbirds, the size of which rarely exceeds 5.7 centimeters, and the weight ranges from 1.6 to 2 g. It is with the egg of this bird that the size of a human fetus can be compared in the sixth week of its development. By the end of the seventh, its dimensions are comparable to those of an ordinary bean.
By the eighth, the fruit can be compared in parameters to an unripe olive, and by the end of the ninth - to a large grape.
At the tenth week, the fetus reaches the size of a candy, which doctors do not recommend that pregnant women eat. 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 to a pea pod, and by the end of the thirteenth - to a ripe fig.
Over the next 7 days, the fruit will grow to the size of an average 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 its length can be compared to an average carrot.
At the 17th week, the fetus can be compared to a medium potato, and at the end of the eighteenth week it can be compared to a large tomato.
Imagine holding a big banana in your hands. This is exactly the size the baby reaches by the end of the nineteenth period. At week 20, it can be compared to a small bunny. Have you ever seen such an exotic fruit as Thai mango? At 21 weeks, the weight of the fetus can be compared with it.
Among penguins, the largest and heaviest are representatives of the Imperial species, whose height often reaches 125 cm and weight - 50 kg. Emperor penguin eggs weigh up to 450 g. This is how much a human fetus weighs at 22 weeks of development.
At week 23, in terms of length, it can be compared with the weight of a corn cob, and by the end of week 24 - with 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 to an average head of broccoli, and by the 27th week - to the weight of a pomelo fruit.
If we take for comparison the length of the baby from the heels to the top of the head, then at 28 weeks it is comparable to the growth of a newborn tiger cub. Most big bird The African ostrich, whose height can reach 200 centimeters and weighs 120 kg, is considered the most popular of the planet. The eggs of these birds weigh on average 1,200 g. This is the weight that is considered normal for a baby at 29 weeks of 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 - with the weight of a newborn lion cub.
In terms of growth, a child at 32 weeks can be compared to a small blue penguin, and by the end of the next period he reaches the weight of an average pineapple. At week 34, the baby acquires the size of a ripe melon with average parameters.
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Monitoring the development of the unborn child
Fetometry is an ultrasound method for determining the size of the fetus, the use of which allows future parents to:
- make sure your child is developing properly;
- find out his gender early;
- enjoy your baby's first smile;
- record his first movements.
Basic diagnostic parameters
With each ultrasound, the specialist issues a conclusion, which must indicate the following fetometric parameters:
- KTR(coccygeal-parietal size) – used on early pregnancy, when assessing the fetus size 20-60 mm. When changing this parameter, the variability is 3-5 days.
- BPR(biparietal size) – used to determine the duration of pregnancy in the second trimester. The accuracy of determining the period is 7-11 days.
- DB(femur length measurement) – the gestational age can also be determined by measuring the femur. The timing accuracy will vary within 2 weeks. DB is used if the BPR cannot be derived satisfactorily.
- coolant(abdominal circumference) allows you to determine the main indicators of child development. The measurement is carried out in a plane in which a short segment of the umbilical vein, fetal stomach, gall bladder, and ductus venosus are visualized. This parameter is the most informative when assessing fetal growth. But it should not be used for macrosomia, that is, when the estimated weight of the fetus already exceeds 4 kilograms.
- OG(chest volume) allows you to determine the gestational age at 14-22 weeks. The accuracy of the indicator varies within 3-4 days.
The simultaneous use of several indicators increases the percentage of accuracy of gestational age. For a period of up to 36 weeks, specialists are guided by the OZ, BPR and DB. After 36 weeks, a combination of coolant, OG and DB is used. However, this approach must be individualized according to asymmetric fetal growth restriction.
Average values of fetometry indicators
There are special tables that indicate normal indicators. As a rule, a pregnant woman is prescribed an ultrasound examination in each trimester, this is at the 12th, 22nd and 32nd weeks. Let's consider the indicators of fetometry tables at these times.
Table of indicators by trimester |
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Trimester | KTE, mm | BPR, mm | DB, mm | Coolant, mm | OG, mm |
You can independently compare your child's indicators with the control table, which shows the average height and weight, as well as biparietal head size, hip and chest diameter, presented below.
Table of average fetometry values by week |
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A week | Height, cm | Weight, g | GBR, mm | DB, mm | DHA, mm |
You should not panic if the indicators in the conclusion do not coincide with the parameters indicated in the table. It shows only average values. In each specific case it is necessary to compare physiological characteristics the unborn child and his parents.
Algorithm for reading indicators
To determine the expected date of birth and the convenience of the doctor, it is advisable to indicate the obstetric gestational age. It is calculated based on the first day of the last menstrual cycle. Fetometry data should also be taken into account. But there may be discrepancies here.
- recalculation of the period based on the 1st day of the last menstruation or the day of conception;
- recalculation of the period based on the results of ultrasound examinations of the 1st or 2nd trimester;
- determination of the percentage level for DG, BPR, J;
- assessment of the likelihood of intrauterine growth retardation.
The need for the procedure
Ultrasound fetometry plays an important role in the diagnosis of malnutrition (intrauterine growth retardation). This syndrome manifests itself when the size of the fetus lags behind the size of the established period by more than two weeks.
The decision about the diagnosis is always made by the doctor. It must take into account the state of health of the pregnant woman, the functioning of the placenta, genetic factors, the position of the fundus of the uterus, etc. Most often, the causes of this pathology are bad habits. expectant mother, infections and chromosomal abnormalities in a child.
Today, this syndrome is treated on an outpatient and inpatient basis. In particular, sanitation of foci of infection, correction of placental insufficiency, formation of a diet, and treatment of complications during pregnancy are carried out.
Ultrasound examination, or ultrasound is an examination method that is widely used during pregnancy at any stage. This diagnostic test is relatively simple, highly informative and safe for both mother and child. The main objectives of ultrasound during pregnancy are:
The following tables provide data on the biometric indicators of the fetus, which are measured at each. They are presented at the 10th, 50th and 95th percentiles. Most often they focus on the 50th percentile, and the rest are considered normal fluctuations.
Dimensions of the fetal head by week of pregnancy
Gestation period, weeks | Fronto-occipital size (LZR), mm | Biparietal size (BPR), mm |
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Abdominal and fetal head circumference
Gestation period, weeks | Abdominal circumference, mm | Head circumference, mm |
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Length of fetal femur and femur bones
Gestation period, weeks | Shin bones, mm | Femur, mm |
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Length of fetal humerus and forearm bones
Gestation period, weeks | Length of forearm bones, mm | Humerus length, mm |
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Norms at the first ultrasound at 10-14 weeks
The first screening ultrasound is performed at 10-14 weeks. Its main tasks are:
- Study of the thickness of the collar zone(the area between the soft tissues covering the spine and the inner surface of the skin, filled with fluid). Assessing the size of the neck fold is very important because... is a fairly accurate way to timely diagnose various chromosomal diseases, in particular Down syndrome. If there is an enlarged nuchal space, the doctor should refer the pregnant woman for consultation with a geneticist. The woman is prescribed additional examination methods: a blood test for alpha-fetoprotein and human chorionic gonadotropin, invasive diagnostic methods (amniocentesis - study of amniotic fluid, placentocentesis - study of placental cells, cordocentesis - study of blood taken from the fetal umbilical cord).
Normal values of the nuchal translucency (NVP) in the first trimester of pregnancy
Gestation period, weeks | Thickness of collar space, mm |
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percentile | 50th percentile | 95th percentile |
|
10 weeks 0 days - 10 weeks 6 days | |||
11 weeks 0 days - 11 weeks 6 days | |||
12 weeks 0 days – 12 weeks 6 days | |||
13 weeks 0 days - 13 weeks 6 days | |||
- Measuring the coccygeal-parietal size (CTP)). This is an important indicator by which you can determine the size of the fetus and the approximate gestational age.
Values of the coccygeal-parietal size by pregnancy
Gestation period, weeks | CTE percentile values, mm |
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10 weeks 1 day | |||
10 weeks 2 days | |||
10 weeks 3 days | |||
10 weeks 4 days | |||
10 weeks 5 days | |||
10 weeks 6 days | |||
11 weeks 1 day | |||
11 weeks 2 days | |||
11 weeks 3 days | |||
11 weeks 4 days | |||
11 weeks 5 days | |||
11 weeks 6 days | |||
12 weeks 1 day | |||
12 weeks 2 days | |||
12 weeks 3 days | |||
12 weeks 4 days | |||
12 weeks 5 days | |||
12 weeks 6 days | |||
13 weeks 1 day | |||
13 weeks 2 days | |||
13 weeks 3 days | |||
13 weeks 4 days | |||
13 weeks 5 days | |||
13 weeks 6 days | |||
Normally, heartbeats should occur at regular intervals, i.e. be rhythmic. Arrhythmia may indicate the presence of a congenital heart defect or fetal hypoxia. The heartbeat should sound very clear and distinct; if there are dull tones, intrauterine oxygen deficiency can be suspected. An important indicator is heart rate.
Normal heart rate by stage of pregnancy
Tachycardia is an increase in the number of heartbeats more than normal, bradycardia is a decrease in heart rate to 120 beats per minute or less. Most often, such changes in heart rate occur during fetal hypoxia as a reaction to a decrease in oxygen in the blood. In such cases, the pregnant woman must be prescribed treatment, which is often carried out in a hospital setting. Therapy is prescribed aimed at improving uteroplacental blood flow and improving intracellular metabolism.
- Assessment of the development and presence of various organs (Bladder, kidneys, liver, stomach, heart), spine, as well as the upper and lower extremities of the fetus. If abnormalities in the development of organs are detected, the woman is referred to a genetic consultation. After a detailed examination, a geneticist decides on the viability of the child and possible termination of pregnancy.
Normal indicators of the second ultrasound at 20-24 weeks
The doctor prescribes a second planned ultrasound at 20-24 weeks. At this time, the following are examined:
- Biometrics(biparietal size, fronto-occipital size, length of tubular bones, abdominal and head circumference). These indicators are measured to assess the growth of the fetus and its size according to the gestational age.
- Detection of various fetal malformations. It is during this period that diagnostics will be the most informative, because during the first examination, the child is still too small, and during the third planned ultrasound it will already be too big; in addition, at longer periods, the placenta may interfere with a thorough examination if it is located on the anterior wall of the uterus.
- Structure, thickness, location and degree of maturity of the placenta. This is the most important organ that supplies the fetus with all the nutrients necessary for its normal development.
Normal thickness of the placenta depending on the stage of pregnancy
Gestation period, weeks | Permissible fluctuations | Normal values, mm |
If the thickness of the placenta increases, the doctor may suspect the presence of (inflammation of the placenta). Making such a diagnosis requires additional examination for the presence of infection and subsequent treatment in a hospital.
Ultrasound also evaluates degree of maturity of the placenta. This is an important indicator characterizing the ability of the “baby place” (synonymous with the term “placenta”) to provide the fetus with the necessary substances.
Degrees of placenta maturity
Gestation period, weeks | Maturity level Doppler testing, tests for possible infections. In the future, the woman must undergo a course of treatment. Drugs are prescribed to treat fetal hypoxia, vitamin therapy, antispasmodics to reduce inflammation, and in the presence of infection, antibiotic therapy. An equally important task for an ultrasound diagnostic doctor is to study placenta attachment site. Most often, the “baby spot” is attached, less often - and even less often - in the bottom area. Normally, the placenta should be 6 cm or more away from the internal os of the cervix. If it is located lower and overlaps the internal os of the uterus, they speak of. This is a serious type of obstetric pathology that threatens the life and health of the woman and child. Often this anomaly occurs in multiparous women, after inflammatory diseases of the uterus, uterine fibroids, and after abortions. The pregnant woman is carefully observed in the hospital or at home, where she must remain completely at rest and abstain from sexual activity. If bleeding begins, immediate hospitalization is required. Quantity and quality of amniotic fluidAverage normal amniotic fluid index values
When the amount of amniotic fluid changes in one direction or another, they speak of polyhydramnios and oligohydramnios. Often found in women with infectious diseases, diabetes mellitus, with some fetal malformations, Rh sensitization (incompatibility of the blood of mother and fetus according to the Rh factor). The condition requires mandatory treatment: antibiotic therapy, drugs that improve uteroplacental blood flow. is a pathological decrease in the amount of amniotic fluid less than 500 ml. The causes of this condition are still unknown. If there is very little water, this may indicate a severe malformation of the fetus: the complete absence of kidneys. There is practically no treatment for oligohydramnios; all therapy is aimed at supporting the child. The ultrasound specialist also evaluates amniotic fluid quality. Normally they should be transparent. If there is turbidity, mucus, or flakes in the amniotic fluid, there is a suspicion of an infectious process. A woman takes tests for hidden infections and undergoing treatment.
Third ultrasound at 32-34 weeksThe third planned ultrasound is performed at 32-34 weeks. Its tasks are:
Normal ultrasound before childbirthUltrasound examination before childbirth is not mandatory for all pregnant women and is carried out selectively according to indications. Its main task is to resolve the issue of the method of delivery. During an ultrasound, the following is determined:
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