Formation of the fetal skeleton. Forms of abnormalities of the fetal skeletal system

A prerequisite for the successful diagnosis of many skeletal defects is that most skeletal bones are detected by echographic examination at the beginning of the second trimester. So, within 12-14 weeks. it seems possible to clearly identify the long tubular bones of the upper and lower extremities, ribs, spine, and bones of the cranial vault. The hands and feet are also accessible for visualization, but the bone elements are very small, making a qualitative anatomical assessment difficult.

In this regard, it is necessary to highlight the main diagnostic criteria indicating a particular pathology of the fetal skeleton. These criteria are usually identified by correctly performing an ultrasound with a mandatory assessment of the anatomical integrity of all extremities, head and internal organs of the fetus.

To correctly diagnose skeletal system defects, the following indicators must be taken into account:

• presence and anatomical integrity of the limb;
• shortening or increasing the length of tubular bones;
• degree of severity of shortening;
• deformation of tubular bones;
• number of bones;
• acoustic bone density;
• condition of soft tissues on the extremities;
• shape and structure of large joints
• shape and structure of the spine;
• limb mobility; visual and subjective

Most of the listed criteria are usually identified during standard biometry or visual assessment of the integrity of the fetal organs. Most bones of the fetal spine can be identified by ultrasound at the beginning of the second trimester of pregnancy, which creates favorable conditions for establishing their presence and quantity. To determine the expected growth of the fetus, it is best to use the V.N. formula. Demidova.

It is important to note that the first echographic signs of bone shortening usually appear after 18-22 weeks. pregnancy. These signs consist in the lag of the length of the tubular bones from the normative indicators by 2-3 mm, which makes it difficult or even impossible to determine the nosological affiliation of the defect and its prognostic significance.

If these disorders are detected, repeat testing is usually recommended at intervals of 4-6 weeks.

During full-term pregnancy, the lag of the length of the tubular bones from the normative values ​​by 4-5 mm is manifested by the height of the newborn 42-46 cm, and in adulthood - 350-160 cm. This category of people among the European population belongs to the group of normal short stature, without pathologies. Consequently, the detection of a slight lag in the size of long tubular bones does not require reflection in the ultrasound protocol in the form of a pathological conclusion.

Lagging length of the femur in the last weeks of pregnancy by 5-8 weeks. in absolute values ​​it is 6-12 mm. The height of newborns with this pathology ranges from 40-44 cm and in general does not exceed 130-140 cm. This category, in terms of its growth indicators, is classified as abnormally short.

Unfortunately, the number of severe childhood dysplasias - severe developmental disorders of the bone apparatus - is constantly growing. A number of television programs are devoted to how difficult it is for people without arms and legs, and for patients suffering from limb deformities. But few people think that they might encounter such a situation in their family.

Fortunately, with the development of ultrasound, limb development abnormalities and others are detected in the early stages of pregnancy.

Appointment with a gynecologist - 1000 rubles. Comprehensive pelvic ultrasound - 1000 rubles. Admission based on test results - 500 rubles. (optional)

Why is the development of fetal limbs impaired?

There are many reasons for the appearance of children with such deformities:

• Hereditary factors. Diseases that cause skeletal deformities are hereditary. An example is achondroplasia - dwarfism caused by underdevelopment and shortening of the legs and arms. In popular programs about the Roloff family, a typical case is shown when people with achondroplasia first have a son, and then a grandson with such a deviation.
• Genetic failuresarising during the process of fertilization or in the first stages of the baby’s development. The cause of deviations can be infections, even common flu, – , , , . It is especially dangerous if the expectant mother had an infection at the beginning of pregnancy.
• Taking certain medications.The most striking example is the thalidomide disaster - the birth in Europe in 1959-1962. 12 thousand children with underdevelopment of limbs. Their mothers were prescribed the anti-anxiety drug thalidomide during pregnancy. Such drugs include antidepressants, drugs that affect blood clotting, some antibiotics, and retinoids used to treat acne. Tragedy happens when an expectant mother takes medication without knowing that she is pregnant or the doctor prescribes a drug that is contraindicated for pregnant women.
• Bad habits and harmful working conditions,affecting heredity. Substances that cause deformities are called teratogenic. These include compounds of arsenic, lithium and lead. Radiation exposure also leads to congenital anomalies. Children with abnormal bone development are born to mothers who abuse alcohol and use drugs. Since hazardous substances and radiation affect the eggs in a woman's body, problems may arise in women who once worked in hazardous industries.

Patients belonging to these groups require careful throughout pregnancy.

What malformations of the limbs are visible on ultrasound?

The baby's bones are visible in the early stages of pregnancy - the femur and humerus - from 10 weeks, the bones of the legs and forearm - from 10 weeks. At this time, you can already count the fingers, see most of the bones of the skeleton and watch how the child moves his arms and legs. Just during this period they carry out .

At 16 weeks, just from the moment , you can measure the length of large bones by assessing fetal development. The size and shape of the limbs are taken into account. A slight curvature of the legs is not an anomaly, but severe deformation is a sign of pathology.

All other parts of the skeleton - the spine, ribs, cranial bones must be correctly developed and not deformed.

The dimensions of the child’s limb bones are shown in the table. It is worth understanding that the indicators are averaged, because Each baby develops individually. The dimensions of the limbs are assessed together with other indicators. Small children have shorter arms and legs than large children.

Duration, weeks	Shin	Hip	Forearm	Shoulder
11-12		5,6-7,3
13-14		9,4-12,4
15-16	15,0-18,0	16,3-20,0	12,0-15,0	15,0-18,0
17-18	21,0-24,0	24,0-27,0	18,0-20,0	21.0-24,0
19-20	27,0-30,0	30,0-33,0	23,0-26,0	27,0-30,0
21-22	33,0-35,0	36,0-39,0	20,0-30,0	30,0-35,0
23-24	38,0-40,0	41,0-44,0	30,0-35,0	38,0-40,0
25-26	44,0-46,0	46,0-49,0	37,0-39,0	43,0-45,0
27-28	47,0-49,0	51,0-53,0	41,0-43,0	47,0-49,0
29-30	51,0-53,0	55,0-57,0	43,0-44,0	49,0-51,0
31-32	55,0-56,0	59,0-61,0	48,0-49,0	55,0
33-34	58,0-60,0	63,0-65,0	50,0-52,0	58,0-59,0
35-36	61,0-63,0	67,0-69,0	54,0-55,0	61,0-62,0
37-38	64,0-65,0	71,0-73,0	55,0-56,0	63,0-64,0
39-40	66,0-67,0	74,0-75,0	57,0-58,0	65,0-66,0

First fetal screening – severe pathologies of fetal development are already visible

At the first screening from 11-14 weeks, most severe deformities of the child associated with improper development of arms and legs can be determined. Often these vices are combined with others .

Pathology of fetal development	Manifestations	Consequences
Amelia	Complete absence of limbs	Children are born without arms and legs, often with defects of internal organs
Ecromelia	Underdevelopment of arms and legs, sometimes accompanied by the absence of hands and feet.	Despite the development of prosthetics, the majority of these children have disabilities
Congenital amputation	One or two limbs are missing	For unknown reasons, underdevelopment of the arm may not be accompanied by other pathologies, but the absence of a leg, as a rule, is combined with other developmental defects.
Adactylia	Missing fingers	The anomaly is often accompanied by underdevelopment or absence of the tongue (aglossia-adactyly), defects of the hard palate and lips. Possible abnormal development of eyelids and jaws
Hemimelia	Shortening or absence of forearm and lower leg bones	The defect is combined with clubfoot and other malformations of the limbs
Phocomelia	Formed feet and hands start immediately from the body, and arms and legs are greatly shortened and non-functional	Even with modern prosthetics, it is not always possible to restore the functions of a child’s limbs.
Clubhanded	Abnormal development of forearm bones	Often combined with heart and spinal defects, it is one of the signs of severe hereditary pathology – Fanconi anemia, manifested by blood clotting disorders, abnormal skeletal development and mental retardation
Lobster claws	Two or four fingers are formed on the arms or legs, separated by a split palm or foot.	The defect is often accompanied by anomalies of facial development - “cleft palate”, “cleft lip”, defects in the development of the eyes and jaws
Radial aplasia	Underdevelopment of the bones of the forearm	It is often a symptom of hereditary syndromes TAR, Aase-Smith, Holt-Oram, in which heart defects, spinal defects, hematopoietic disorders and mental retardation are diagnosed. Most of these children die at an early age

Pathologies of fetal development - severe combined dysplasia

In hereditary pathologies detected starting from the 15th week, defects in the development of skeletal bones are combined with other defects. Most babies die in utero, immediately after birth and during the first years of life. In this case it happens or is discovered . With some diseases, children with disabilities can live a long time.

Disease	Symptoms	Forecast
Thanatophoric dysplasia	Significant shortening of the limbs, narrow chest, large head with a prominent forehead. The hips are curved like a telephone handset. Sometimes the hips are straight and the skull is shaped like a clover.	Bad. Babies are stillborn or die after birth
Osteogenesis imperfecta	Multiple limb deformities. After birth, prone to fractures	Children die at an early age or remain disabled. There is a delay in physical development
Ellis-van Creveld syndrome	Shortening of limbs, abnormal development of hands, dwarfism, brittle bones.	More than 50% of children die. Survivors have serious health problems caused by underdevelopment of the genitourinary and cardiovascular systems
Achondrogenesis	Multiple anomalies of skeletal development - short limbs, underdeveloped spine, ribs, lower jaw,	Babies are stillborn or die after birth
Achondroplasia	The fruit has a large head with prominent frontal tubercles and short limbs. The most common form of dwarfism	Does not affect life expectancy. Such people can even have offspring, but in 50% of cases their children will inherit the anomaly
Jarcho-Levin syndrome	Anomalies in the development of vertebrae and ribs, compressed short chest, “crab-shaped” chest, head “pressed” into the shoulders, disproportionately short torso	Children often die from lung problems. Survivors have disabilities
Dystrophic dysplasia	The child is developmentally delayed, having small height and weight. Long bones are shortened, arms and joints are deformed	Most patients have disabilities. because due to underdevelopment of bones they cannot move independently

If a child has skeletal development abnormalities

If obvious severe abnormalities are detected, the doctor will suggest . Otherwise, the woman will have to face the birth of a child with an incurable hereditary disease.

• amniocentesis - analysis of amniotic fluid;
• chorionic villus biopsy - collection of chorionic membrane cells;
• placentocentesis – collection of placental tissue;
• cordocentesis - examination of blood from the umbilical cord.

The detection of gene abnormalities in the fetus predicts the birth of a child with severe disability, sometimes incompatible with life. Of course, each woman decides for herself whether to keep such a child. But it must be taken into account that the majority of children with genetic diseases that affect not only the skeletal system, but also internal organs, despite treatment, die at an early age.

The decision must be fully informed. It is no secret that mothers who decide to give birth to a baby with serious pathologies often do not realize the gravity of the situation. In this case, it is better to trust the opinion of doctors.

Where is expert ultrasound performed to detect fetal defects in St. Petersburg

You can undergo such an examination during pregnancy at the Diana clinic in St. Petersburg. The price of a fetal ultrasound depends on the stage of pregnancy and starts from 1300 rubles. Appointment with a gynecologist based on ultrasound results - 500 rubles. The cost of a medical abortion is 3,500 rubles.

Shortening of limbs includes shortening of the entire limb (micromelia), proximal limb (rhizomelia), middle limb (mesomelia) and distal limb (acromelia). To diagnose rhizomelia and acromelia, it is necessary to assess the correspondence of the sizes of the humerus and femur to the sizes of the bones of the forearms and legs.

For some skeletal dysplasia the structure of the hands and feet is disrupted. The term "polydactyly" describes conditions in which there are more than five fingers on a limb. A distinction is made between postaxial polydactyly, when the extra finger is localized on the side of the ulna or fibula, and preaxial polydactyly, when it is on the side of the radius or tibia. Syndactyly is the fusion of soft tissue or bone tissue of adjacent fingers, and clinodactyly is the curvature of one or more fingers. The most common spinal abnormality found in skeletal dysplasia is platyspondyly, which consists of flattening of the vertebral bodies.

There are case reports in the literature diagnostics in the antenatal period, kyphosis and scoliosis of the spine, as well as hemivertebrae and frontal clefts of the vertebral bodies.

Biometry of fetal skeletal bones

Measurement length of tubular bones fetus is widely used in obstetric practice to determine the duration of pregnancy. In nomograms used for this purpose, long bone length is the independent variable and gestational age is the dependent variable. However, this also represents an important difference; in nomograms used to assess whether bone length corresponds to normal values ​​for the corresponding period, gestational age is already used as an independent variable, and bone length is used as a dependent variable.

So to get it right use With nomograms of this type, the researcher must accurately know the true gestational age of the fetus. In this regard, pregnant women at risk for the development of skeletal dysplasia in the fetus should be recommended to begin observation in prenatal diagnostic centers from the early stages of pregnancy in order to be able to use all clinical methods for determining the gestational age of the fetus. For patients with an unspecified gestational age, indicators of the relationship between the length of the limbs and the circumference of the fetal head can be used.

Some researchers for this purpose, biparietal size is taken as an independent variable, however, measuring head circumference has the advantage since this indicator does not depend on its shape. The weakness of this approach is that it is based on the assumption that the bones of the fetal skull are not involved in the pathological process, which cannot but be the case with some forms of skeletal dysplasia.

Nomograms and the figures in our articles present the mean values ​​of limb bone lengths and their 5- and 95-percentile confidence intervals. It must be remembered that when using such upper and lower limits, 5% of potentially healthy fetuses in pregnant women from the general population are outside their limits when assessed using these nomograms. It is probably most preferable to use the 1st and 99th percentiles of limb bone lengths for the corresponding gestational ages as confidence limits, which would correspond to more stringent criteria.

Unfortunately, it has not yet been carried out works, the number of patients examined would ensure a significant difference between the indicators for the 5th and 1st percentile. However, most skeletal dysplasias that can be diagnosed prenatally or neonatally are characterized by marked shortening of the long bones, and given this circumstance, the difference between using boundaries at the 5th percentile level compared with the 1st is not so decisive.

The exception is the heterozygous form achondroplasia, in which the length of the limbs is only moderately reduced until the third trimester of pregnancy. In this case, abnormal development can be detected by a change in the slope of the growth curve of the femur. In a study by L Gonçalves and P. Teanty, based on 127 observations of 17 types of various dysplasias, a discriminant analysis was carried out, showing that the length of the femur is the best biometric parameter that can be used to make a differential diagnosis among the five most common diseases: tanatophoric dysplasia , osteogenesis imperfecta type II, achondrogenesis, achondroplasia and hypochondroplasia. S. Gabrieli et al. assessed the possibility of early diagnosis of skeletal dysplasia in high-risk patients.

In their research 149 women were included with an uncomplicated singleton pregnancy in the period from 9 to 13 weeks, counting from the last menstruation, who were examined using transvaginal scanning. Using the polynomial regression method, the relationship between femur length and gestational age, as well as between biparietal and coccygeal-parietal dimensions was assessed. Eight patients who had a history of giving birth to children with skeletal dysplasia were examined at 2-week intervals until 10-11 weeks of gestation. A strong correlation was found between femoral length, coccygeal-parietal and biparietal dimensions.

In the first trimester it was diagnosed only two of five cases of skeletal dysplasia (both were recurrent cases of osteogenesis imperfecta and achondrogenesis). This study suggested that assessing the correlation of femur length with coccygeal-parietal size and femur length with biparietal size in the first trimester may be useful in the early diagnosis of severe forms of skeletal dysplasia. In cases of milder forms of this pathology, biometry is of limited value.

Fetus is an unborn child in the mother's womb. In medicine, it is generally accepted that the embryo develops in the first two months, and then, before birth, the fetus.

The fetal skeleton begins to form literally from the first days of conception. Already on the second day, the fertilized egg, which actively divides and grows rapidly, forms special cells - ectoderm. From the ectoderm, bone tissue and skeletal bones develop in the future.

Human skeleton- an extremely important component of our body. Bones support the body, determine its shape and size, and protect internal organs from injury. Bone tissue is involved in mineral metabolism in the body, the skull protects the human brain, bone marrow influences the immune system, and the main processes of hematopoiesis occur in it.

General information about fetal skeletal development

70% of bones consist of particularly strong bone tissue containing large amounts of mineral salts. These are mainly: calcium, magnesium and phosphorus. Of course, in addition to them, other elements are needed for the proper formation of skeletal bones - aluminum, copper, selenium, fluorine, zinc, but in much smaller quantities. The fetus takes all these substances from the mother’s body, so it is important that a pregnant woman eats a nutritious and varied diet that contains “building material” for the child.

If necessary, the doctor can additionally prescribe vitamins and microelements. These recommendations should not be neglected: if the fetus does not receive the necessary substances for the formation of bones, the skeleton may form abnormally.