PRENATAL AND PERINATAL PATHOLOGY
Prenatal periodic the period of fetus development beginning with the moment of fertilization to the birth of the child. Normally, prenatal period lasts for 40 weeks (280 days). If the child is born on the 36th week or earlier, he (she) is premature, if the term is more than 40 weeks, over mature. Fetal pathology, which occurs in this period, is called prenatal pathology.
The case of fetal death before the 14th week of gestation is called abortion, that within the period of \A—28 weeks is called late abortion. If the fetus dies on the 28th week or later (until the delivery or during it), the case is called mortinatality.
Main pathologic conditions of the prenatal period are classified according to the periods of the embryo development:
Prenatal period is subdivided into 2 periods:
• progenesis—period of maturation of ovum and sperm;
• kymatogenesis — period of development of fertilized ovum.
There are several periods in the kymatogenesis:
• blastogenesis — (from the 1st to 15th day);
• embryogenesis — (from the 16th to 75th day);
• fetogenesis — (from 76th to 280th day).
Development of each pathology is connected with the termination period in which the causative agent acts. Pathologic conditions formed in a period of progenesis are called gametopathy.
If this occurs during blastogenesis, it is called blastopathy, during embryogenesis — embryopathy, during fetogenesis —fetopathy.
Each organ has its own period of teratogenic factor action. This period is called teratogenic termination period.
Gametopathyis an injury of ovum and sperm during ovo- and spermatogenesis until fertilization. Gametopathy occurs in gene mutations, chromosomal aberrations. At present about 150 autosomal recessive genetic defects and 200 defects with autosomal dominant inheritance are known. There are also defects connected with sex X chromosome. Chromosome mutations are called chromosomal aberrations. The most frequent is mongolism (trisomia of the 2 lth pair), Patau's syndrome. The former occurs once per 600— 700 cases, the latter per 5149 cases.
Blastopathiesoccur during the first 15 days from the moment of fertilization.
The most frequent cause of blastopathy is chromosomal aberration in combination with harmful effect of environmental factors.
Manifestations of blastopathies are different: 1) superficial or deep implantation of blastocyst (causes defects of development, shape, localization of placenta); 2) disturbance of embryo orientation (umbilical cord defects are the most frequent);
3) empty embryo sacs (blastocytes without an embryo);
4) embryopathy of twin monstrosity, diplopagus (symmetrical accretion of twins), heteropagus (one of the twins is underdeveloped). Teratomas are considered to be as asymmetric monsters.
Depending on the place of accretion the following types of pagi are distinguished: craniopagus, thoracopagus, inguinopagus, etc. Usually they cannot live.
Defects of placenta development
1. Placenta hypoplasia (normal mass is 0.5— 0.7 kg), placenta/fetus ratio is 1/5—1/7. When the mass of the placenta decreases, fetus hypoplasia develops.
2. Defects of placenta localization are marginal and central placenta presentation in respect to internal uterus orifice. This develops as a result of Mastopathy, its causes are unknown. It presents a risk of placenta detachment during the delivery and intranatal death of the fetus.
3. Defects of placenta detachment are placenta adhesion (caused by deep implantation of blastocyst). The placenta does not detach after the delivery. Hemorrhage may occur. Operative intervention (in some cases uterus amputation) is indicated.
4. Placenta abruption. This occurs at extragenital and genital maternal pathology. It may result in intranatal fetus asphyxia.
5. Umbilical cord defects (its normal length is 0.5—0.7 m). If the length is less than 0.5 m, the cord is short, more than 0.7 m it is long.
6. Disturbance of the umbilical cord attachment to the placenta:
• central and eccentric are normal types of attachment;
• membranous is pathological one, when the umbilical cord is attached to the membranes, its vessels may be compressed with the parts of the fetus and amniotic fluid which may cause their rupture, ante-and intranatal fetus death may occur.
7. Amnion development defects: — hydramnion (2 1 and more), oligoamnios (500 ml and less).
Embryopathyis the pathology developed within the period of 16—75 days. According to the WHO, their frequency is 1.3%. It has increased up to 7% recently. Any congenital defect may manifest as one of the following changes:
1) absence of any organ or part of the body (agenesis, aplasia, acrania, anencephalia);
2) underdeveloped organ (hypoplasia of lungs, thymus, chondrodystrophy);
3) overdeveloped organ (hyperplasia of thymus, adrenal glands);
4) changes in the shape of the organ (double stomach, ball-like heart);
5) changes in the organ localization (dextrocardia);
6) preserved embryonic organ. Classification of congenital defects.
1. According to the character of involvement:
• isolated (one organ);
• systemic (several organs of one system);
• multiple (in different organs and systems) (facial and cerebral skull, feet, hands).
2. According to localization:
• central nervous system;
• cardiovascular system;
• alimentary tract;
• urinary system, etc.
Central nervous system and cardiovascular system are most frequently involved because these systems have the longest teratogenic terminal period, from the 18th day to the 50th day.
3. According to the etiology. This is the most perfect classification. But as the etiology of the majority of defects is not known this classification is not frequently used. According to its etiology there are several types of embryopathy: alcohol, thalidomide, rubeolar, genetic, chromosomal.
Among CNS defects there are:
• anencephalia (absence of brain substance);
• acrania (absence of the bones of cranial vault);
• microcephalia (hypoplasia of the brain);
• microgyria (increase of gyrus number when their size is decreased);
• porencephalia (different cysts connected with lateral ventricles);
• congenital hydrocephalia (inner and outer);
• cyclopia (rare defect, one orbit is in the area of the mouth);
• brain hernia.
Main congenital heart defects:
1. Congenital defect of heart cavities division:
• defect of interventricular septum;
• defect of interatrial septum;
• absence of interventricular or interatrial septum: three-chamber heart.
2. Congenital defect of arterial trunk division:
• common arterial trunk;
• complete transposition of the main vessels;
• stenosis and atresia of pulmonary artery;
• stenosis and atresia of aorta;
• open Botallo's duct.
3. Combined heart defects:
• Fallot's triad, tetrad, pentad.
Fallot triad consists of: 1) interventricular septum defect, 2) stenosis of the pulmonary artery, 3) hypertrophy of the right heart.
Fallot tetrad consists of: 1) interventricular septum defect, 2) stenosis of the pulmonary artery, 3) hypertrophy of the right hear, 4) aorta dexraposition.
Fallot pentad consists of: 1) interventricular septum defect, 2) stenosis of the pulmonary artery, 3) hypertrophy of the right heart, 4) aorta dexra-position, 5) defect of interatrial septum.
Fetopathies,mainly non-infectious, are very frequent.
The main noninfectious fetopathies are hemolytic disease of the newborn, diabetic fetopathy, macrosomia.
Large fetus (macrosomia) is one weighing 4.0 kg and more at birth. When the mass is 5.0 kg, the fetus is called giant. The problem of the giant fetus is very important at present. During the recent 60 years the incidence of giant fetus has increased 4 times.
At present 5.2—14.4% of the children are large at birth.
Large fetus affects both the health of the mother and that of the fetus. Complications of the large fetus delivery occur 8 times more frequent. They are rupture of the maternal passages, abnormal loss of blood during the delivery (> 250 ml), disjunction of the pelvic bones, post-term delivery, hydramnion, nephropathy. The children suffer from immune deficiency, i.e. exudative diathesis, rachitis, frequent respiratory infections, severe septic diseases. Birth injury may occur. Therefore, perinatal death rate in large fetus is 2—3 times higher than in the normal ones.
Diabetic fetopathy is the disease of the fetus due to maternal prediabetes and diabetes. As a rule, the
body mass is A—6 kg. The skin is purple cyanotic with small point hemorrhages, the neck is short, and the face as well as the soft tissues of the back and chest are swollen.
The signs of immaturity are observed in the mature fetus: Beclard's nucleus (nucleus in the lower epiphysis of the femur); in mature children it is 5— 7 mm, if it is less than 5 mm or absent, the fetus is immature) is absent, erythroblastosis in the liver and kidneys is observed. Hepatomegaly and cardiomegaly can be seen. Microscopic examination demonstrates islets of Langerhans hypertrophy, increased amount of β-cells, fat degeneration of the liver, glycogen accumulation in the tubular epithelium in the kidneys, hydropic degeneration of the myocardium. During the delivery of the child with fetopathy, hypoxia due to placenta vascular sclerosis and disturbance of placental circulation may occur. Hyalin membrane disease may develop because synthesis of surfactant is disturbed due to disturbed lipid exchange (lipoproteid).
The death is caused by antenatal and intranatal asphyxia, respiratory insufficiency, birth injury, hypoglycemia after birth stress.
The main infectious fetopathies are cytomegaly and congenital toxoplasmosis.
Cytomegaly (from cytos — cell and megalos — large) is a virus infection involving salivary glands. The disease is characterized by formation of giant cells with intranuclear inclusions.
Generalized form of infection develops in the newborns. DNA-containing virus enters the organism of the fetus from the mother through the placenta. Generalized infection in children is characterized by CNS involvement, which is not observed in acquired cytomegaly. Encephalitis with formation of cytomegalic cells, perivascular infiltration and calcinosis foci in the subependymal zone is observed in children. These phenomena cause hydrocephalia. Cytomegalic cells measuring 30—40 μm contain intranuclear formation resembling «owl's eye». They can be found in the lungs, kidneys, liver, intestine, pancreas, adrenal gland, thymus. Hemorrhages and necroses can also be observed in these organs. The disease lasts several days (sometimes weeks). It ends with death caused by damage to vitally important organs.
Congenital toxoplasmosis is a disease caused by toxoplasma. It develops as a result of hematogenic transfer from the mother's organism. Toxoplasma is a protozoic microorganism from tripanosomid family. The source of human infection is dogs and cats. The fetuses are infected through the maternal placenta.
During teratogenic termination period, ebryo-pathy incompatible with life occurs.
Fetopathy may be early and late. In early fetopathy, the child has phenomena of brain damage. In late fetopathy, the newborns have marked meningoencephalitis.
In infection during the delivery, generalized form develops.
Pathology. Early fetopathy: microcephalia of brain, porencephalia with gliosis (consolidation of the remained brain tissue) and calcinosis. Microscopic examination demonstrates cysts filled with granular spheres. Late fetopathy: foci of necrosis and calcinosis in the brain, pseudocysts and free parasites, marked encephalitis in the whole brain, meningopathy; ependymatitis — hydrocephalus. Productive necrotic rhinitis and uveitis in the retina.
Generalized form: besides CNS involvement there is hepato- and splenomegaly, jaundice, ulcers of the intestine, myocarditis, interstitial pneumonia.
Microscopic examination demonstrates erythroblastosis in the liver and spleen, necrosis, calcinosis and lymphohistiocyte infiltration in the liver, myocardium, kidneys, cholestearosis in the liver. Outcome: death of fetuses and newborns or complication (paralysis, mental retardation, blindness).
Perinatal periodis the period before and after the delivery, beginning from the 28th week of gestation (196th day) to the 1st week of extrauterine life. This is at the 28th week of gestation when the fetus mass reaches 1 kg and the length of the body — 35 cm. This fetus can live. Delivery of a smaller fetus is termed abortion.
Perinatal period and the respective pathology and mortality is divided into antenatal (before the delivery), intranatal (during the delivery) and postnatal, or neonatal (6 days).
Perinatal mortality is mortinatality and mortality within the first 7 days of the life.
On an average 23 newborns of 1000 die during the first year of the life (in Japan only 5 of 1000).
Morphological signs of immaturity and over-maturity in newborns
In immature newborns, the body mass is less than 2.5 kg and body length is less than 45 cm, gestation period is 36—37 weeks. Signs of immaturity are lanugo on the face, shoulders, back, soft floor of the auricle, underdeveloped nails, soft cranial bones. This signs can be determined at physical examination.
Significant criterion of fetus immaturity is absence of Beclard's nucleus in the lower epiphysis of the femur. In mature children it is 5—7 mm. If it is less than 5 mm or absent, the fetus is immature.
Microscopic examination of the organs allows to determine the degree of immaturity. In immature fetus, embryonic glomeruli are noted in the superficial layer of the cortical substance of the kidneys. Erythroblastosis foci are observed in the kidneys and liver. There is thickening of interalveolar septa in the lungs. Sprout zone in the brain is widened.
Overmature fetus is born at the 41st week of gestation and later. The main signs of overmaturity are dry desquamative skin, general fetus hypotrophy, dense long floors of the auricle, very dense cranial bones. Amniotic fluid, umbilical cord, membranes are usually colored with meconium as the fetus experiences
intrauterine hypoxia. Significant morphological criterion is Beclard's nucleus (0.8 cm and more).
Asphyxiais connected with oxygen deficiency and is characterized by disturbance of respiration and blood circulation. Asphyxia may be antenatal, intranatal and postnatal. First two types of asphyxia are caused by various factors causing disturbance in fetus supply with oxygen (winding round with umbilical cord, nodes of umbilical cord, detachment and presentation of the placenta, maternal diseases). Postnatal asphyxia develops in a newborn at disturbance of independent respiration. As a rule, postnatal asphyxia is a continuation (or consequence) of intranatal asphyxia. When during the delivery CNS (including respiratory center) is damaged or under the influence of intrauterine hypoxia, the fetus makes the first inspiration intrauterinally (carbon dioxide stimulates the respiratory center) and amniotic content is aspirated. In this case the lungs cannot spread after the delivery, postnatal asphyxia develops. One of the causes of asphyxia in a newborn is a birth injury of the spinal cord and central nervous system.
Pathology. The main clinico-morphological syndroms of asphyxia are as below:
1. Hemorrhagic syndrome (vascular plethora in the inner organs, fluid blood in the heart chambers, diapedesis hemorrhage to the brain substance, adrenal glands as well as subpericardial and subepicardial-
hemorrhages). The hemorrhages are due to hypoxia, on one hand, and development of syndrome of intravascular dissemination of blood clotting, on the other hand, resulting in fibrin thrombi in the micro-circulatory bed.
2. Edema syndrome (pericellular and perivascular edema of the brain substance, pia mater, myocardium interstitium).
3. Dystrophic changes in the liver, kidneys, myocardium, brain substance.
4. Aspiration of amniotic fluid containing skin epithelium, lanugo, meconium.
If such children survive, they may experience disturbance of psychomotor development due to CNS damage, cardiosclerosis due to dystrophy and micro-necroses.
Pneumopathyis lung disease which occurs as a rule in immature children.
The immature lung lacks antiectatic factor (surfactant) which is necessary for spreading the lung during the inspiration and which prevents the lungs collapse during the expiration. Surfactant is lipoproteid which is produced by alveolar epithelium. Electron microscopic study demonstrates it only in mature children. In the immature lung the activity of fibrinolytic properties of the lung tissue due to immaturity of its fibrinolytic enzymes.
Atelectasis is not spread at birth or collapsed during the lifetime lung. Atelectasis of underdeveloped lung are called primary, those of the lung which breathed before are called secondary.
In the newborns the total atelectasis and disseminated primary atelectasis when the areas of air alveoli interchange with the collapsed alveoli may be observed. Atelectasis in the lungs of the newborn may be due to asphyxia and birth injury caused by the damage the respiratory center as well as aspiration of amniotic fluid. The lung drowns in the water. Microscopic examination demonstrates collapsed alveoli.
Edematous hemorrhagic syndrome is associated with asphyxia when the lung capillaries are overfilled with the blood, vascular permeability increases due to hypoxia. Diffuse edema and large intra- and extra-alveolar hemorrhages develop. The breathing is difficult, the children die of respiratory insufficiency. This condition is often accompanied by the disease of hyalin membranes. Autopsy demonstrates large lungs with hemorrhages. Microscopic examination shows intraalveolar pink fluid, hemorrhages.
Hyalin membrane disease is formation of protein masses colored bright pink with eosin in the parietal alveoli. The disease is often associated with either atelectasis or edematous hemorrhagic syndrome. Both lungs are involved, asphyxia develops quickly, the newborns die within the period of 24—36 hours.
Autopsy demonstrates dense red-cyanotic plethoric lungs.
Microscopically, eosinophilic masses in the parietal alveoli, the rest of the tissue is atelectatic. Recently, hyalin membrane disease has been noted in mature children with mature surfactant. It is a jatrogrenic pathology which develops during the intensive care as with this purpose the air containing more than 20% of oxygen is used. Aspiration syndrome is the first inspiration done in uterus. Amniotic fluid may be infected or may contain meconium. The syndrome is due to hypoxia, is often observed at overmaturation. If the children may breath independently, pneumonia develops during 3—5 hours (its etiology is colon bacillus, Klebsiella, cocci). In massive aspiration, total or disseminated atelectasis of the lungs (primary) may develop as the lungs are filled with aspiration masses and do not spread.
Pneumonia of newbornsis an infectious disease which is characterized by a definite mechanism of infection and the background against which the disease develops.
Pneumonia of newborns may occur in uterus (in ante- and intranatal periods) as well as after the birth. The etiology is different. The most frequent are coccus pneumonias, Klebsiella, colon bacillus. The disease often develops against a background of amniotic fluid aspiration both infected and not infected.
If the child survives for 3—5 hours, small-focus pneumonia develops, in 24 hours it turns into confluent pneumonia. Microscopically, leukocyte monocyte infiltration of alveolar tissue involving the bronchioles and bronchi is observed. Elements of amniotic fluid are determined in the exudate. It is considered that intrauterine pneumonia is responsible for the death during the first 2—3 days of life.
Birth injuryis damage to the fetal tissues and organs with mechanical forces during the delivery. Birth injury should be differentiated from obstetric injury, which occurs when obstetric manipulations are carried out.
The causes of birth injury are due to:
• the state of the fetus;
• the state of the maternal passages;
• the course of the delivery.
The state of the fetus: 1) embryopathy, Mastopathy (defects of development), 2) fetopathy accompanied by hemorrhagic syndrome, 3) immaturity (the tissues are easily ruptured) overmaturity—hypoxia-increased vulnerability of the fetus.
The state of the maternal passages: 1) rigidity of the birth canal tissue, 2) pelvis defects (narrow pelvis, rachitic pelvis), 3) tumors of maternal passages, 4) oligoamnios, hydramnion.
The causes depending on the dynamics of the labor: 1) precipitated delivery, 2) prolonged delivery.
Pathology. In cephalic presentation, the most frequent injuries are intracranial and spinal ones which cause death in the newborns (about 8—20 % of deaths according to the Kharkiv Perinatal Center). The least severe is soft tissue labor tumor and cephalohematoma. The former occurs in cephalic presentation in parietal and occipital lobes. It is characterized by edema, petechial hemorrhages. It disappears within 1—2 days.
Cephalohematoma is hemorrhage under the periosteum of the cranial bones. It is always localized in one bone. It disappears slowly. When infected, it may become a source of purulent meningitis. The most severe intracranial injury is hemorrhage to the meninges and brain substance.
All hemorrhages are divided into: 1) epidural, 2) subdural, 3) subarachnoid, 4) intracephalic.
Epidural hemorrhages are located between the bones of the skull and the dura mater (inner cephalohematoma).
Subdural cepalohematomas occur in rupture of the falciform process and cerebellum tentorium. The blood is accumulated under the dura mater on the brain substance.
Subarachnoid cephalohematoma is localized between the arachnoid and pia mater. It occurs in rupture of the falciform process, cerebellum tentorium, veins.
Intracerebral cephalhematomas are the hemorrhages to the vascular plexi of the brain, under the ependyma of the lateral ventricles with rupture to the ventricles.
The most frequent course of the death in intracranial injury is rupture of the falciform process and cerebellum tentorium. Of birth injuries, the most frequent are spinal injuries (often fatal to the life), fracture of the clavicle occurring in large fetuses, subcapsular hematomas of the liver.
Less frequent are hemorrhages to the adrenal glands, mainly unilateral.
Hemolytic disease of the newbornis severe fetopathy occurring due to the action of the mother's antibodies on the organism of the fetus and the newborn. The cause of HDN is rhesus incompatibility of the mother's and fetal blood (Rh-negative mother and Rh-positive fetus). The rhesus factor is located in the erythrocytes of the fetus, it passes through the placenta to the mother's blood and causes anti-rhesus antibody production. The mother's antibodies destroy the fetal erythrocytes.
HDN occurs in fetuses from the 2nd and the following pregnancies, as the mother's immunization increases. HDN may occur when the blood group of the mother and the fetus are incompatible.
Classification of HDN:
1. General congenital edema.
2. Congenital anemia of the newborn.
3. Severe jaundice of the newborn.
In early massive immunization of the mother, early fetopathy develops. The fetus dies before the birth, on the 5th—7th month of gestation.
When the mother's immunization is later and more moderate, the child is born alive with one of the forms of HDN.
Edematous form: edema of skin, subcutaneous fat, meninges and brain substance, there is transude in the cavities. The liver is enlarged, the spleen is 4—6 times bigger. The heart is enlarged due to the myocardium hyperplasia. The lungs and the thymus are diminished.
Microscopically: erythroblastosis in the liver, spleen, lymphatic nodes, kidneys. Embryonic glomeruli in the kidneys of mature newborns.
Anemic form is frequent in immature fetuses. The skin and mucous membranes are pale. Jaundice is absent. The liver and spleen are slightly enlarged. Microscopic study reveals erythroblastosis in them. The children may die of associating pneumonia.
Icteric form is evident by the end of the first day. The disease develops quickly. Exchange transfusion is necessary to prevent the death of the child. Autopsy demonstrates bilirubin encephalopathy (indirect toxic bilirubin enters the brain damaging ganglion cells). They die mainly in hypocampus, nuclei of hypothalamus and cerebellum. The cells are colored ocher-yellow. They are seen against pale background. The state is called nuclear jaundice. The liver and spleen are enlarged, they have the signs of erythroblastosis and hemosiderosis. There are bilirubin infarcts in the kidneys.
The children who survived HDN may develop defects of the CNS development (including complete idiopathy) in future.
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