Malformations

The causes of 40-60% of developmental anomalies are unknown. The term "sporadic birth defects" is used to denote an unknown cause, accidental occurrence and low risk of recurrence in unborn children. For 20–25% of anomalies, the “multifactorial” cause is more likely to be the complex interaction of many small genetic defects and environmental risk factors. The remaining 10–13% of the anomalies are associated with environmental influences. Only 12-25% of anomalies have purely genetic causes.

Teratogenic factors

The action of teratogenic factors depends on the dose. For each factor, there is a certain threshold dose of teratogenic effects. Usually it is 1-3 orders of magnitude lower than lethal. Differences in teratogenic effects in different biological species, as well as in individuals of the same species, are associated with features of absorption , metabolism , and the ability of a substance to spread in the body and penetrate the placenta .

The most studied teratogenic factors:

Alcohol

The alcoholism of the parents, especially the mother, matters. Maternal drinking during pregnancy can lead to fetal alcohol syndrome

Infectious diseases transmitted from mother to fetus

In cases where the causative agents of infections have a teratogenic effect, it is not possible to evaluate the threshold dose and dose-dependent nature of the action of the teratogenic factor.

A number of viral diseases transferred during pregnancy: ( rubella , mumps , inclusion cytomegaly ).

Ionizing Radiation

X-rays , exposure to radioactive isotopes can have a direct effect on the genetic apparatus. In addition to direct action, ionizing radiation also has a toxic effect and is the cause of many congenital anomalies.

Medicines

It should be noted that there are no drugs that can be considered completely safe, especially in the early stages of pregnancy.

Nicotine

Smoking during pregnancy can lead to a child lagging behind in physical development.

Nutrient Deficits

Deficiencies in a number of nutrients ( iodine , folate ^[1] , myo-inositol ^[2] ) are proven risk factors for neural tube defects (such as spina bifida ) and congenital heart defects ^[3] . The use of folic acid for the prevention of congenital malformations is one of the most proven means of primary prevention of congenital malformations ^[4] . For more information, see the article “ Primary prevention of congenital malformations ”.

The formation of defects occurs mainly during the period of embryonic morphogenesis (3-10th week of pregnancy ) as a result of a violation of the processes of reproduction, migration, differentiation and cell death. These processes occur at the intracellular, extracellular, tissue, interstitial, organ and interorgan levels. Violation of cell reproduction explain hypoplasia and aplasia of organs. Violation of their migration is the basis of heterotopies. Delay in cell differentiation leads to immaturity or persistence of embryonic structures, and its complete stop - aplasia of an organ or its part. Violation of physiological cell death, as well as violation of adhesion mechanisms (“bonding” and fusion of embryonic structures), are the basis of many dysraphia (for example, spinal hernias).

Experimental embryology has proved that the so-called. teratogenetic termination period, that is, the length of time during which the teratogenic agent can cause a congenital malformation. This period is different for different organs. Using the data of embryology, one can judge the timing of the occurrence of a particular malformation and draw up teratological calendars for malformations of different organs.

The formation of developmental defects can also be based on a stop of development during a critical period, a violation of the formation process, or dysontogenesis, and tissue destruction. In this case, underdevelopment of organs or their parts ( hypogenesis ) or their excessive development ( hypergenesis ), absence of organs or body parts ( agenesis ), improper position or movement of organs, or incorrect formation of one or another tissue ( dysplasia ) can occur.

There are double (multiple) malformations, which are based on irregularities in the development of two or more fruits, and single, associated with a violation of the formation of one organism. Double malformations, or deformities, are “undivided” twins , among whom thoracopagi, xyphopagus, pygopagus, etc. are distinguished depending on the area of ​​their connection. Single malformations include acrania , congenital clefts of the upper lip, cleft soft and hard palate , polydactyly , congenital heart defects . Prevention of malformations - a system of antenatal protection of the fetus.

“Malformations” is a broad category that includes various conditions: minor physical abnormalities (such as birthmarks ), serious disorders of individual systems (such as congenital heart defects or limb defects ), and combinations of anomalies affecting several parts of the body. Congenital metabolic defects are also considered congenital malformations.

There are 3 main types of birth defects:

1. Congenital physical abnormalities
2. Congenital metabolic errors
3. Other genetic defects

The relationship of congenital malformations with sex

In many studies, it was found that the incidence of certain congenital malformations depends on the gender of the child (table). ^{[5] [6] [7] [8] [9]} For example, pyloric stenosis and the clavate foot are more common in boys, while congenital hip dislocation is 4-5 times more common in girls. Among children with one kidney, about two times more boys , while among children with three kidneys, about 2.5 times more girls. The same picture is observed among newborn children with an excess number of ribs, vertebrae, teeth and other organs that underwent a reduction in the number and oligomerization during the evolution process - there are more girls among them. Among newborns with their shortage, on the contrary, there are more boys.

Anencephaly is twice as common in girls. ^[10] Excessive muscles are 1.5 times more likely to be found in the bodies of men than women. The number of boys born with the 6th finger is 2 times the number of girls. ^[eleven]

P. M. Raevsky and A. L. Sherman analyzed the incidence of congenital malformations depending on the body system. The predominance of males was noted for malformations of phylogenetically younger organs and organ systems ^[12] .

In terms of etiology, gender differences can be divided into those appearing before and after the differentiation of male gonads in the process of embryonic development, which begins from the eighteenth week. The testosterone level in male embryos increases significantly. ^[13] Subsequent hormonal and physiological differences in male and female embryos may explain some gender differences in the incidence of congenital malformations.

Sex ratio of patients with congenital malformations

Congenital malformation	The ratio of sexes, M: W
Female-dominated vices
Congenital hip dislocation	1 : 5.2 [12] ; 1 : 5 [14] ; 1 : 8 [9]
Anencephaly	1 : 1.9 [12] ; 1 : 2 [10]
Craniocerebral hernia	1 : 1.8 [12]
Spinal Hernia	1 : 1.4 [12]
Lung aplasia	1 : 1.51 [12]
Esophageal diverticulums	1 : 1.4 [12]
Stomach	1 : 1.4 [12]
Neutral defects
Underdevelopment of the tibia and femur	1 : 1.2 [12]
Atresia of the small intestine	1 : 1 [12]
Esophageal atresia	1.3 : 1 [12]
Male-dominated vices
Cleft lip	2 : 1 [14]
Pyloric stenosis	5 : 1 [14] ; 5.4 : 1 [9]
Meckel diverticulum	More common in boys [12]
Colon diverticula	1.5 : 1 [12]
Rectal atresia	1.5 : 1 [12]
Bilateral renal agenesis	2.6 : 1 [12]
Unilateral renal agenesis	2 : 1 [12]
Bladder exstrophy	2 : 1 [12]
Congenital obstruction of the renal pelvis and congenital malformations of the ureter	2.4 : 1 [9]
Congenital Megacolon ( Hirschsprung's Disease )	More common in boys [12]
All malformations	1.29: 1 [9]

See also ICD-10: Class XVII : Congenital malformations (blood defects), deformations and chromosomal abnormalities.

A

• Lung agenesis
• Bilateral renal agenesis
• Unilateral renal agenesis
• Acrania
• Albinism
• Anencephaly
• Lung aplasia
• VACTERL Association
• Atresia of anus
• Esophageal atresia
• Jejunum atresia

B

• Clavate foot

In

• Cleft palate
• Congenital cesspool
• Congenital Hip Dislocation ( Hip Dysplasia )
• Congenital Cretinism
• Congenital Megacolon (Hirschsprung's Disease)
• Congenital heart defects

G

• Hydrocephalus
• Lung hypoplasia
• Hernias

D

• Meckel's diverticulum
• Esophageal diverticulums

E

G

3

• Cleft lip

And

To

• Clubfoot
• Cryptorchidism

L

• Lymphatic malformation

M

• Megacolon
• Microcephaly

H

• Underdevelopment of the tibia and femur

About

• Omphalocele

P

• Pyloric stenosis
• Polydactyly
• X chromosome polysomy
• Polythelia
• Genital defects

P

C

• Syndactyly
• Down Syndrome
• Klinefelter Syndrome
• Clippel Syndrome - Feil
• Cat scream syndrome
• Patau Syndrome
• Shereshevsky's syndrome - Turner
• Edwards Syndrome
• Spinal hernia

T

U

Uterus Doubling

F

• Fibrodysplasia
• Fetal alcohol syndrome

X

C

• Cyclopia

H

• Craniocerebral hernia

Прав

E

• Bladder exstrophy
• Ectrodactyly
• Epispadias

Yu

I

• International Classification of Diseases
• List of hereditary diseases
• Congenital heart defects
• Anomalies in the development of female genital organs

• Dyban A.P., Essays on pathological human embryology, L., 1959
• Russell LB, The effect of radiation on the intrauterine development of mammals, in the book: Radiobiology, trans. from English., M., 1960
• Potter E ,, Pathological anatomy of fetuses, infants and young children, trans. from English., M., 1971.

• CDC's National Center on Birth Defects and Developmental Disabilities