Characteristics of the premature infant

Since 1961, on the recommendation of the WHO, all newborns weighing less than 2500 g have been designated as "low birth weight" newborns. At present, this position is not shared by many researchers, as it eliminated the concepts of "prematurity" and "intrauterine development period" when assessing the condition of the child. Many researchers divide newborns with low birth weight into three groups:

1. newborns whose intrauterine growth rate was normal until birth (body weight corresponds to gestational age);
2. children born at term or post-term, but having a body weight that is insufficient for the given gestational age due to intrauterine growth retardation;
3. premature babies who, in addition, had a slowdown in intrauterine growth, i.e. their body weight was insufficient due to both prematurity and impaired intrauterine development.

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The reason for the birth of premature babies

In most observations, intrauterine growth retardation in primigravidas was due to morphofunctional features of the placenta and development of placental insufficiency. Comparative analysis of qualitative indicators and quantitative characteristics showed that at birth at 28-32 weeks, half, and at birth at 33-36 weeks - only one third of the placentas had anomalies in shape and attachment of the umbilical cord. In cases where pregnancy was threatened with termination in the first trimester, changes in the placenta were more pronounced. Thus, the resorption surface area of the placenta decreased to 3.1 m2 ^at a pregnancy term of 28-32 weeks and to 5.7 m2 ^at a term of 33-36 weeks.

When using general review methods of morphological examination in the placenta of women who gave birth prematurely, a number of changes were revealed, which include massive fibrinoid deposits in the decidual plate and intervillous space with the presence of single X-cells, areas of calcification, an increase in the number of altered terminal villi (sclerotic, edematous, fibrinoid-altered), and a narrowing of the intervillous space. All these changes characterized dystrophic processes and were more often found in the placentas of women who gave birth before 32 weeks. At the same time, a large number of unchanged terminal villi with syncytial "nodules" of the proliferative type, with dilated, full-blooded and subepithelially located capillaries were determined. These villi caused compensatory-adaptive reactions in the placenta. These features were more often detected in the placentas of women who gave birth after 33 weeks of pregnancy. Stereometric analysis of placentas confirmed the prevalence of dystrophic processes in placentas during births before 32 weeks and compensatory-adaptive changes during births at later stages. In women who had acute respiratory viral diseases during pregnancy, histological examination of placentas, in addition to the above changes, revealed pronounced disorders of uteroplacental blood circulation in the form of extensive hemorrhages into the decidual plate, intervillous space and stroma of the villi.

When analyzing the morphometric data of the placentas and comparing them with the data on the condition of premature infants at birth and in the early neonatal period, it was found that the body weight of newborns, the weight and morphometric parameters of the placenta depending on the gestational age are reduced in cases where children were born with signs of intrauterine growth retardation. The condition of children born with signs of hypotrophy was assessed according to the Apgar scale, as a rule, below 5 points. In the morphological analysis of the placenta, more pronounced in intensity and prevalence of dystrophic processes were noted in those women whose children were born with signs of hypotrophy and before 32 weeks of pregnancy. These data were confirmed by stereometric analysis of the structural elements of the terminal villi, where a decrease in the relative areas of the intervillous space was observed. If during the histological examination compensatory changes in the placentas prevailed over dystrophic ones, then the physical data of the children were normal and corresponded to the gestational age.

Electron microscopic examination of the placentas revealed changes in all cellular structures of the villous chorion: syncytiotrophoblast, stroma of the villi, and capillaries. Microvilli covering the syncytiotrophoblast were absent in places or unevenly distributed on the altered terminal villi. The ultrastructure of sclerotic villi was characterized by an increase in the number of collagen fibers in the stroma, running in different directions, and edematous villi by a decrease in the number of cellular components with large electron-optically transparent formations of various shapes and numerous partitions. The number of collagen fibers around the capillary confirmed the presence of vascular sclerosis. At the same time, the endothelial cells lining the inner surface of the capillary were changed. Their nuclei were elongated, the nuclear chromatin was compactly located along the periphery, sometimes with destruction of the cytoplasm. All these changes in the cellular elements of the terminal villus confirmed the presence of a dystrophic process in the placentas. Electron microscopic examination of the placentas also revealed an increase in subepithelial vessels and hyperplastic capillaries, changes in the density of microvilli, and the appearance of grouped nuclei of syncytiotrophoblast with swollen mitochondrial cells in the syncytium.

As a result of the study of the enzymatic activity of ATPase and 5'-nucleotidase in placentas in premature births, a dependence of the reaction product on changes in various structures of the terminal villus was established. Thus, high enzymatic activity was observed on microvilli, secreting pinocytotic vesicles, nuclei of syncytium, cytotrophoblast and endothelial cells, i.e. unchanged terminal villi, where the processes were more often of a compensatory nature. Thus, where destruction was revealed during the ultrastructural study of the placenta, the enzymatic activity of ATPase and 5'-nucleotidase was reduced. This was especially true for edematous, sclerotic and fibrinoid-altered villi. Electron microscopic study made it possible to once again determine the prevalence of dystrophic or compensatory processes in the placentas of women who gave birth prematurely. The results of ultrastructural and ultracytochemical studies confirmed that the changes occurring in the placenta indicate the development of placental insufficiency.

Thus, morphofunctional studies of placentas in premature births, conducted using morphometric and electron microscopic methods, made it possible to detect the phenomena of placental insufficiency. In cases of prevalence of compensatory-adaptive processes in placentas over dystrophic ones, pregnancy proceeded favorably and premature babies were born with physical parameters corresponding to the gestational age. In cases of pronounced dystrophic changes in placentas, the development of placental insufficiency led to intrauterine growth retardation of the fetus, complicated course of the neonatal period in premature babies and was one of the indications for early termination of pregnancy.

The main signs of a premature baby

A child born before 38 weeks of pregnancy is considered premature. Children with a birth weight of more than 2500 g are diagnosed with prematurity, according to the international nomenclature (Geneva, 1957), if they were born before 37 weeks.

Classification of prematurity based on gestational age at birth

• I degree - 35-37 weeks of pregnancy.
• II degree - 32-34 weeks of pregnancy.
• Stage III – 29-31 weeks of pregnancy.
• Stage IV - less than 29 weeks of pregnancy.

Premature infants are characterized by a higher rate of weight and length gain in the first year of life (except for the first month). By 2-3 months they double their initial weight, by 3-5 months they triple it, and by one year they increase it 4-7 times. At the same time, extremely immature infants are significantly behind in absolute growth and weight indicators ("miniature" infants), 1-3 "corridor" of centile charts. In subsequent years of life, deeply premature infants may maintain a peculiar harmonic "delay" in physical development. Physical development is assessed using the scale of G.M. Dementyeva, E.V. Korotkaya and the method of E.A. Usacheva, taking into account gestational age.

The neuropsychic development of premature babies is usually slowed down in the first 1.5 years, the degree of this delay depends on the severity of prematurity, this is a kind of "norm" for immature children. In the absence of damage to the nervous system, even extremely immature children by 2-3 years of age do not differ in the level of psychomotor development from full-term children, although many of them retain emotional lability, fatigue and rapid exhaustion of nervous processes.

Anatomical and physiological characteristics of premature babies

The features of the neurological status of stage I premature infants (35-38 weeks) without factors aggravating the neurological status do not differ from those of full-term infants. In children with stage II-IV prematurity, the morphological status depends on the degree of brain maturity. For children with stage II-III prematurity, respiratory failure (rhythmic shallow breathing) is characteristic, persisting up to 2-3 months of life. By 1.5-2 months of life, the "heat loss" syndrome, marbled skin pattern, cyanosis, rapid cooling, and edema syndrome are expressed.

Children are sluggish, motor reactions are reduced. Concentration and initial tracking reactions begin to form with satisfactory weight gain and the absence of somatic diseases, appear from 1.5-2 months of life. Muscle hypotonia is characteristic up to 2-4 weeks, then replaced by increased tone in the flexors of the limbs.

Unconditioned reflexes from the group of spinal automatisms (reflexes of support, automatic gait, crawling, etc.) begin to manifest themselves from 1-2 months of life. In prematurity of III-IV degree, it is difficult to objectively assess the neurological status up to 1.5-2 months, since the leading syndrome is general lethargy, characteristic of CNS depression.

It is important to remember that with improper rehabilitation, even mild clinical manifestations at the age of up to 3-4 months of life may subsequently progress.

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Features of the neurological status in premature infants

Premature babies are defined as a risk group for psychoneurological pathology. A pediatrician should pay attention to clinical manifestations of psychoneurological status. In a premature baby, the syndrome of increased neuroreflex excitability occurs in one of three ways.

In the first case, the clinical picture in the acute period is similar to the condition of a full-term child, subsequently decreases and gradually disappears by 6-12 months. In the second variant, after a year of life, asthenoneurotic syndrome is formed. In the third variant of the course, minimal manifestations of the syndrome of increased neuroreflex excitability are transformed into a convulsive syndrome (regardless of age). Such conditions practically do not occur in full-term children with the syndrome of neuroreflex excitability.

Thus, minimal clinical changes in the nervous system of a premature baby can have irreversible severe consequences, which requires constant dynamic monitoring by a pediatrician and specialists using instrumental research methods.

Most often, premature babies develop hypertensive hydrocephalic syndrome, which occurs in two variants. Favorable course - at first, hypertensive symptoms disappear, and later, no signs of hydrocephalus appear. Unfavorable course - the outcome is cerebral palsy, hydrocephalic and convulsive syndromes.

The syndrome of CNS depression is typical for children with III-IV degree of prematurity. It indicates not only neurological but also somatic problems, is typical for subarachnoid and parenchymatous hemorrhages, bilirubin brain damage, occurring with conjugation jaundice in immature premature children.

Convulsive syndrome may be observed in the first days of life. Its clinical picture is typical. Sometimes in the recovery period, after 4-6 months of life, there are attacks of apnea, sharp reddening or cyanosis of the face, marbled skin pattern, Harlequin symptom, increased sweating, regurgitation, nodding movements of the head or bending of the body forward and backward. These prognostically unfavorable symptoms may first appear against the background of intercurrent diseases, indicating irreversible changes occurring in the central nervous system. All premature babies are characterized by the syndrome of vegetative-visceral dysfunctions, the severity of which depends on the degree of prematurity, timeliness and volume of rehabilitation measures.

A child born prematurely shows signs of immaturity: body weight less than 2500 g, body length less than 45 cm, a lot of cheesy grease, insufficient development of subcutaneous fat, fluff on the body (normally it is noted only on the shoulder girdle), short hair on the head, soft ear and nasal cartilages, nails do not extend beyond the fingertips, the umbilical ring is located closer to the pubis, in boys the testicles are not lowered into the scrotum, in girls the clitoris and labia minora are not covered by the labia majora, the child's cry is thin (squeaky).

The maturity level is assessed using a special scale (WHO, 1976). The period of intrauterine development of the newborn can be assessed with an accuracy of up to 2 weeks. When assessing the maturity level, the period of pregnancy at which the birth occurred should be taken into account.

The Apgar scale was proposed for full-term newborns, but this scale can be successfully used for prematurity as well. The increased frequency of suppression of vital parameters in premature babies correlates with low assessments of the condition at birth. According to many researchers, with a body weight of up to 1500 g, the condition is assessed by the Apgar scale from 0 to 3 points in approximately 50% of newborns, while with a weight of 3000 g - only in 5-7% of newborns. The assessment of the child's condition by the Apgar scale 5 minutes after birth has great prognostic value. If it remains low, the prognosis is unfavorable.

In recent years, it has been established that the fetus makes respiratory movements in utero, which can be recorded using ultrasound equipment. If these movements are absent or significantly weakened, then newborns are more likely to develop hyaline membrane disease. In case of nephropathy or diabetes in the mother, the frequency of episodes of respiratory movements in the fetus decreases. Intrauterine respiration is a new parameter that will apparently allow a more accurate assessment of the fetus's readiness for extrauterine respiration. The mechanism of the first breath is quite complex, and the role of stimuli in this process has not been sufficiently studied, especially in children born at different gestational ages. Asphyxia, which can be observed as a short episode at the time of birth, is of great importance in the excitation of the respiratory center at the time of birth. A decrease in PO2 and pH, an increase in PCO2 stimulate respiratory movements, causing impulses from the carotid and aortic chemoreceptors. Such short episodes of asphyxia, which are observed during normal labor, are characterized by the absence of metabolic acidosis. Prolonged asphyxia is accompanied by the appearance of metabolic and respiratory acidosis and leads to depression of the respiratory center.

Another important stimulus for the onset of breathing is a sharp drop in the temperature of the environment surrounding the child at birth. The decrease in temperature stimulates the nerve endings in the child's skin, these stimuli are transmitted to the respiratory center. They are an intense stimulator of breathing. However, excessive cooling of the newborn leads to profound suppression of the child's vital activity. Tactile stimulation created by ordinary touching of the child at the moment of birth also stimulates the onset of breathing. The end result of the extrauterine activity of the respiratory muscles is the creation of a lower pressure inside the lungs of the fetus than in the atmosphere. Negative intrathoracic pressure promotes the flow of air into the lungs. The diaphragm plays a major role in the normal functioning of the lungs.

Adaptation of the cardiovascular system to extrauterine life occurs simultaneously with adaptation of the lungs. Expansion of the lungs and adequate oxygenation, which occur in the child with the onset of respiratory movements, cause a decrease in arterial pressure in the pulmonary circulation due to the expansion of the pulmonary arterioles. At this time, arterial pressure in the systemic circulation increases significantly due to the shutdown of placental blood flow. As a result of the change in the ratio of arterial pressure values, conditions are created for the elimination of mixing of venous and arterial blood, the oval window and the arterial and then venous duct close.

To assess respiratory function at birth and in the following days, the Silverman scale is increasingly used, according to which the respiratory function of the newborn is characterized by:

• movement of the chest and retraction of the anterior abdominal wall during inhalation;
• retraction of intercostal spaces;
• retraction of the sternum;
• the position of the lower jaw and the participation of the wings of the nose in the act of breathing;
• character of breathing (noisy, with groaning).

Each of these symptoms is assessed from 0 to 2 points as its severity increases. The sum of the points gives an idea of the respiratory function of the newborn. The lower the score on the Silverman scale, the less pronounced the manifestations of pulmonary insufficiency. When nursing premature babies, it is necessary to maintain adequate breathing and normal lung function. It is especially important not to disrupt the mechanism of the first breath, so all manipulations to suck mucus from the upper respiratory tract should be carried out extremely carefully.

Maintaining an optimal ambient temperature is one of the most important aspects of effective care for a premature baby. Premature babies have anatomical features that predispose them to heat loss, and their thermal balance is less stable than that of larger babies.

Newborns with low body weight have a relatively large body surface. A large body surface causes more extensive contact with the external environment, increasing heat loss. Heat loss per unit of mass in a premature baby weighing 1500 g is 5 times greater than in an adult. Another anatomical obstacle to heat conservation is a too thin layer of subcutaneous fat, as a result of which heat is quickly transferred from the internal organs to the surface of the skin.

The baby's posture also affects the rate of heat loss. When the limbs are bent, the body surface area and, accordingly, heat loss are reduced. The tendency to bend the limbs increases with the duration of intrauterine development. The shorter it is, the more heat the newborn loses. These factors significantly affect the newborn's ability to survive, the rate of recovery after asphyxia, the effectiveness of therapy for respiratory disorders, and the rate of weight gain.

Under the influence of cold, the rate of heat loss increases due to the activation of metabolism in the newborn. This phenomenon is observed in both full-term and premature newborns, although the rate of heat loss is somewhat lower in the latter. The main metabolic disorders in newborns exposed to cooling include hypoxemia, metabolic acidosis, rapid depletion of glycogen stores, and a decrease in blood sugar levels. Increased metabolism entails an increase in oxygen consumption. If the oxygen content in the inhaled air is not increased, then the PO2 of the blood decreases. In response to hypothermia, norepinephrine is released, which leads to a narrowing of the pulmonary vessels. In this regard, the effectiveness of pulmonary ventilation decreases, which leads to a decrease in the partial pressure of oxygen in the arterial blood. In this case, the breakdown of glycogen and its conversion into glucose occur under hypoxic conditions, and during anaerobic glycolysis, the rate of glycogen breakdown is many times higher than during aerobic glycolysis, resulting in hypoglycemia. In addition, during anaerobic glycolysis, a large amount of lactic acid is formed, which leads to an increase in metabolic acidosis.

These disorders occur more quickly, the more premature the child is, since the glycogen reserves are insignificant, and are especially reduced in newborns with insufficient oxygenation due to atelectasis due to immaturity of the lungs and other respiratory disorders. For such newborns, maintaining the thermal regime of the environment is of vital importance. Body temperature drops immediately after birth. To a certain extent, this is a physiological process, since stimulation of the skin receptors is necessary to stimulate the first breath. In a normal delivery room, the temperature of a full-term newborn decreases by 0.1 °C in the rectum and by 0.3 °C on the skin per minute. In a premature baby, these losses are even more significant, especially if there is a respiratory disorder at the same time.

A significant amount of heat is lost when amniotic fluid evaporates from the baby's body. To reduce these losses, a premature baby should be received in warm diapers, wiped down and placed on a table heated from above by a heat source, or in an incubator heated to 32-35 °C. Maintaining the thermal regime in the first days of life is a priority task when nursing premature babies.

Premature infants do not cope well with stressful situations that arise due to the onset of extrauterine life. Their lungs are not mature enough to perform gas exchange, and their digestive tract cannot digest 20-40% of the fat contained in milk. Their resistance to infection is low, and the increased rate of heat loss disrupts thermoregulation. Increased capillary fragility predisposes to hemorrhages, especially in the ventricles of the brain and the cervical spinal cord. The most common diseases that premature infants are predisposed to are hyaline membrane disease, intracranial hemorrhages, infection, and asphyxia.

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Complications in premature babies

The most severe complication of the postnatal period of life in a premature baby is hyaline membrane disease, or respiratory distress syndrome. Most often, this disease is observed in children with a birth weight of 1000-1500 g and less. In most cases, newborns have surfactant in their lungs, which ensures effective breathing. A small amount of it is produced with the participation of methyltransferase from 22-24 weeks of intrauterine life. After birth, the production of surfactant by this pathway ceases under the influence of hypoxia. Synthesis of surfactant by a more stable system with the participation of phosphocholine transferase begins at 34-35 weeks of intrauterine life; this system is more resistant to acidosis and hypoxia. At birth and shortly thereafter, a premature baby can breathe without difficulty, but because surfactant is being used up and the new system is synthesizing it in small quantities, normal functional residual capacity of the lungs is not established. The alveoli, which inflate during inhalation, collapse during exhalation. Each subsequent breath requires incredible effort from the baby.

As the child weakens, atelectasis increases, which leads to the development of hypoxia and hypercapnia. Since the anaerobic pathway of glycolysis prevails, metabolic acidosis occurs. Hypoxia and acidosis increase vascular spasm, as a result of which the blood flow to the lungs decreases. Hypoxia and acidosis lead to damage to capillaries and necrosis of the alveoli. Hyaline membranes from the products of cell death are formed in the alveoli and terminal respiratory bronchioles, which in themselves, without causing atelectasis, significantly reduce the elasticity of the lungs. These processes further disrupt the production of surfactant. Insufficient straightening of the lungs and the preservation of high resistance of the pulmonary vessels lead to an increase in arterial pressure in the pulmonary circulation, as a result of which the intrauterine type of circulation (oval window, arterial duct) is preserved. The action of these extrapulmonary shunts is expressed in the diversion of blood from the lungs, and: the child's condition progressively worsens. In case of a threat of premature birth and at the time of birth, it is necessary to prevent hyaline membrane disease in the child (maintaining the temperature regime, sufficient oxygenation, combating acidosis). Modern methods of intensive care can significantly reduce mortality in this disease. In the neonatal period, premature babies show signs of intrauterine growth retardation. Such conditions are most typical for children born to mothers with extragenital pathology and toxicosis in the second half of pregnancy. At the same time, as our studies have shown, children with signs of hypotrophy are often born even to primigravida women without any other complications of the pregnancy. Hypotrophy is detected more often in premature births at 28-32 weeks of pregnancy (67%). In births at 33-36 weeks, the frequency of birth of children with signs of intrauterine growth retardation is only 30%.

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Examination of premature babies by specialists

In the first month, the child is examined by a neurologist, ophthalmologist, otolaryngologist; all children born prematurely undergo audiological screening. Children born with a body weight of 1500 g or less, as well as all premature babies who were on intensive care or artificial ventilation, are shown to undergo indirect binocular ophthalmoscopy to detect signs of retinopathy.

Mandatory laboratory and instrumental research methods

• General blood test at 1 and 3 months, in the second half of the year.
• General urine analysis at 1 and 3 months, in the second half of the year.
• Coprological examination twice a year.
• Blood bilirubin is monitored for up to 1 month, then as indicated.
• Neurosonography at the age of up to one month, then as indicated.
• Ultrasound of the hip joints at the age of up to 3 months.

According to the indications:

• biochemical blood tests;
• computed tomography and magnetic resonance imaging.

In the future, it is necessary to draw up an individual schedule of dispensary observation depending on the degree of prematurity and the clinical and functional characteristics of the corresponding health groups.

Tactics of care of premature infants in pediatric area

Premature babies are usually monitored during the first year of life according to the scheme provided for children of the 2nd and 3rd health groups.

Outpatient monitoring of premature babies in a polyclinic setting involves differentiated monitoring of their physical and neuropsychic development, peripheral blood indices, as well as systematic examinations by specialists (neurologist, orthopedist, ophthalmologist, and, if indicated, surgeon, allergist, etc.).

The daily routine is individually prescribed with a delay of 2-4 weeks or more compared to peers, taking into account the clinical picture.

The feeding pattern is planned individually. In case of natural feeding, additional prescription of fortifiers is mandatory (Pre-Semp, Frizland Foods, FM-8, Breast milk fortifier), which are specialized protein-mineral or protein-vitamin mineral supplements. Adding fortifiers to the diet eliminates the deficiency of nutrients. It is possible to introduce artificial mixtures based on whey protein hydrolysates (Nutrilak Peptidi MCT, Alfare, Nutrilon Pepti MCT) in a volume of 20-30% of the requirement. In case of artificial feeding of premature babies, specialized mixtures are used (Pre NAN, Pre Nutrilak, Per Nutrilon, Humana-O-GA).

Health and hardening procedures are carried out depending on the severity of developmental disorders.

Adequate prevention of rickets and anemia and development of an individual vaccination schedule are necessary.

Premature babies are at risk for morbidity, infant mortality and childhood disability, as irreversible changes in the central nervous system, often combined with congenital malformations, cannot be ruled out.

Vaccinations are carried out according to an individual schedule depending on the child's health. Most premature babies do not receive the BCG vaccine in the maternity hospital. The question of when to start vaccination is decided strictly individually, starting at 2 months of age. As a rule, due to perinatal CNS lesions and frequent development of anemia, premature babies receive the BCG vaccine (or BCG-M) after 6 months; subsequent vaccinations, depending on the child's health, are carried out in combination (polio vaccine + ADS-M) or separately; the pertussis component (DPT vaccine) is used extremely rarely in premature babies due to its greatest reactogenicity. The first vaccination - BCG, as a rule, is carried out when the body weight reaches 2200 g. In case of severe CNS lesions, vaccinations are postponed until 6 months.

The pediatrician determines the time of vaccination together with the neurologist, taking into account the risk of allergic reactions, and assesses the completeness of the immune response. Vaccinations for children with altered reactivity are often carried out "under the cover" of antihistamines.

At all stages of observation of a premature baby, active joint work of the doctor and parents is necessary. In the first days and weeks of the newborn's life, the mother, as a rule, needs psychotherapeutic correction, relief of postpartum stress.

The doctor of the children's clinic and the visiting nurse monitor the conditions of the child's home life, the timeliness of medical interventions (visits to specialists, tests, vaccinations, classes to stimulate psycho-emotional and speech development. Physical methods are important for rehabilitation: various massage complexes, gymnastics, exercises in water, dry immersion, music therapy, aromatherapy.

An appropriate, gentle home environment and regular activities with parents, sensory stimulation (toys, lullabies), music therapy, and training in basic skills are essential conditions for the full development of premature babies.

For monitoring, the child's family is given scales at home. Nutrition calculations are carried out once every 2 weeks. Patronage by a doctor and a nurse according to an individual schedule during the first month, and then, depending on the state of health, is carried out at home or in a clinic.