Premature infants

　　Since the mechanism of labor onset is not fully understood, there are still many unknowns about the causes of preterm birth. In clinical case analysis, the main causes of preterm birth are as follows:

　　1. Hypertensive diseases in pregnancy.

　　2. Premature rupture of membranes, placental abruption, or placenta previa.

　　3. Multiple pregnancies or excessive amniotic fluid.

　　4. Chronic diseases such as heart disease, kidney disease, nephritis, liver disease, diabetes, severe pulmonary tuberculosis, endocrine disorders (such as habitual preterm delivery), malnutrition, and so on.

　　5. Anemia and severe hemolytic diseases.

　　6. Acute infectious diseases with high fever.

　　7. Uterine tumors, endometritis, and relaxation of the cervix.

　　8. Pelvic and vertebral deformities, twins or fetal malformations, premature rupture of the amniotic membrane, abnormal umbilical cord, and excessive amniotic fluid.

　　9. Acute or chronic poisoning.

　　10. Violent emotional fluctuations or overexertion.

　　11. Accidents or surgery.

　　Most complications in preterm infants are related to the immaturity of organs and systems, as follows:

　　1. Lung:The amount of surfactant produced usually does not meet the needs to prevent alveolar collapse and incomplete lung expansion, which will lead to respiratory distress syndrome.

　　Due to insufficient coordination of suckling and swallowing reflexes, newborns born before 34 weeks may require intravenous nutrition or tube feeding. The immaturity of the brainstem respiratory center leads to episodes of apnea (central apnea). Apnea can occur due to obstruction in the pharynx alone (obstructive apnea) or combined central apnea (mixed apnea). Bleeding in the periventricular embryonic layer of the preterm infant's brain may enter the ventricle (intraventricular hemorrhage). Periventricular white matter infarction (periventricular white matter necrosis) may be caused by several reasons that are not yet fully understood. Hypotension, insufficient cerebral blood perfusion, or unstable blood pressure, or a sudden rise in blood pressure (such as rapid intravenous injection of fluid or colloid) can cause cerebral infarction or hemorrhage.

　　2. Infection:The incidence of sepsis or meningitis in preterm infants is almost four times that of full-term infants. Intravenous catheter placement, tracheal intubation, skin breakdown, and significantly low levels of serum immunoglobulins in preterm infants increase the likelihood of infection. Preterm infants are the only ones susceptible to necrotizing enterocolitis.

　　3. Thermoregulation:Premature infants have a large surface area to body volume ratio, so when exposed to an environment below the neutral temperature, they will quickly lose heat and find it difficult to maintain normal body temperature.

　　4. Gastrointestinal tract:Premature infants have a very small stomach capacity, immature suckling and swallowing reflexes, which hinder adequate feeding through the mouth or nasogastric tube and pose a risk of respiratory aspiration. Most premature infants can tolerate breast milk, and can also use special infant formula milk or specially prepared premature infant formula containing 24kcal/30ml. Small premature infants can be successfully fed with their mother's milk through a nasogastric tube. Breast milk contains immunological factors and nutritional factors that are lacking in modified milk formulas. However, for very low birth weight infants (<1.5kg), breast milk cannot provide sufficient calcium, phosphorus, and protein, and they need to be fed with different mixed fortified breast milk formulas.

　　On the first or second day of life, if sufficient fluid and calories cannot be provided by mouth or through a nasogastric tube or nasoduodenal tube due to the condition of the premature infant itself, a 10% glucose solution containing electrolytes can be administered intravenously to prevent dehydration and malnutrition. In small, sick premature infants, especially those with respiratory distress or frequent apnea, continuous feeding of breast milk or formula milk through a nasoduodenal tube or gastric tube can satisfactorily maintain the intake of calories. Start with a small amount of half-strength formula milk; if tolerated, gradually increase the quantity and concentration over 7~10 days. In very small or critically ill premature infants, sufficient nutrition can be provided by total parenteral nutrition through peripheral venous infusion, percutaneous or surgical placement of a catheter.

　　5. Kidneys:The renal function of premature infants is not mature, and their ability to concentrate and dilute urine is worse than that of full-term infants. Feeding with high-protein formula milk, the accumulation of fixed acids caused by skeletal growth, and the insufficient ability of immature kidneys to excrete fixed acids can all lead to delayed metabolic acidosis and growth retardation, accompanied by the loss of sodium and bicarbonate in urine. Therefore, it may be necessary to supplement bicarbonate orally for several days (1~2mEq/kg per day, given in 4~6 doses).

　　6. Hyperbilirubinemia:Premature infants are more prone to hyperbilirubinemia than full-term infants. Even with serum bilirubin levels below 10mg/dl (170μmol/L), small, sick premature infants can develop kernicterus. The high bilirubin levels in premature infants are partly due to the underdeveloped excretion mechanism of the liver, including defects in the uptake of bilirubin from plasma, insufficient ability of hepatocytes to generate conjugated bilirubin with glucuronic acid, and inadequate ability to excrete bilirubin into the bile ducts. Reduced peristalsis allows bilirubin glucuronic acid to be converted into unconjugated bilirubin by the intestinal enzymes β-glucuronidase in the intestinal lumen, thereby increasing the reabsorption of free bilirubin (enterohepatic circulation of bilirubin). Conversely, early feeding increases peristalsis, thereby reducing the reabsorption of bilirubin, and can significantly reduce the incidence and severity of physiological jaundice. In rare cases, delayed clamping of the umbilical cord can lead to the input of a large number of red blood cells, increased red blood cell destruction and bilirubin production, which can significantly increase the risk of hyperbilirubinemia.

　　The earlier the premature infants are born, the thinner and more tender their skin becomes, with more tissue water content, concave pressure marks, red color, less subcutaneous fat, fewer muscles, and shorter nails. At the same time, the body hair on the trunk becomes longer, and the hair on the head becomes less and shorter, with a larger head, wider fontanelles, flat and soft ear shells adhering to the skull, soft chest, and pinpoint areolas without prominent edges, small or un palpable breasts. The abdomen is more bloated, and the scrotum is underdeveloped. The testicles of male premature infants are often in the inguinal canal and gradually descend into the scrotum during development. Female premature infants have more separated and prominent labia minora. There are fewer creases on the soles of the hands and feet.

　　Premature infants have difficulty and instability in thermoregulation, and the use of their heat-generating effects is limited. They have fewer muscles, low muscle tone, and cannot change their posture to reduce the area of heat loss. Their resistance is weak, and they have very weak resistance to various infections, and even minor infections can lead to serious consequences such as sepsis. Premature infants breathe fast and shallowly, and often have irregular intermittent breathing or apnea. Their ability to suckle and swallow is weak, the cardiac sphincter is relaxed, and they are prone to coughing, vomiting, diarrhea, and abdominal distension.

　　When trauma, hypoxia, infection, and coagulation mechanisms are impaired, it is often easy to bleed and the bleeding may be severe. The brain vessels are especially prone to injury and bleeding. Sometimes, unexplained pulmonary hemorrhage may also occur. Premature infants have poor conjugation and excretion of bilirubin, and their physiological jaundice lasts longer and is more severe than that of full-term infants. Due to the immature liver of premature infants and incomplete liver function, factors such as prothrombin V, VII, and X are lower than those of full-term infants, so the coagulation mechanism is not sound and bleeding is easy.

　　Premature infants have reduced iron and vitamin A, D storage, and are prone to this kind of nutritional deficiency. Due to the immaturity of the glomeruli and renal tubules, the glomerular filtration rate is low, and the clearance rates of urea, chlorine, potassium, and phosphorus are also low, with more common proteinuria. Premature infants experience a significant weight loss after birth and are prone to acid-base imbalance due to infection, vomiting, diarrhea, and changes in environmental temperature. The central nervous system is immature, with weak crying, less activity, low muscle tone, and unclear reflexes. Reflexes such as coughing, suckling, and swallowing are poor.

　　Premature birth is the main cause of neonatal illness and death, and among the various causes of preterm birth, most are due to maternal factors, among which, except for congenital reproductive malformations, most can be prevented through prenatal care.

　　Prenatal examinations should be given great importance, especially for high-risk groups who should receive early and appropriate perinatal care. For example, the prevention and control of preeclampsia-eclampsia, the reduction of the incidence of placental abruption, the early treatment of placenta previa, and the correction of anemia. Pregnant women with heart disease should be strengthened in management, and common knowledge of prenatal care should be popularized, with preventive measures such as avoiding infection. The use of labor relaxation methods to prevent preterm labor, and providing sufficient time, so that corticosteroids can be used to promote lung maturation before delivery.

　　Premature infants can undergo blood tests, CT scans, chest X-rays, and other examinations.

　　1. Blood glucose test

　　The child can undergo blood glucose tests to check for symptoms of hypoglycemia or hyperglycemia in premature infants.

　　2. EEG examination

　　Some premature infants are prone to intraventricular hemorrhage or periventricular leukomalacia, which can be diagnosed by brain imaging.

　　3. CT scan

　　CT scans can observe signs of intracranial lesions in premature infants.

　　4. Detection of antigens and antibodies

　　5. Blood tests

　　Blood tests include white blood cell count and neutrophil count, hemoglobin concentration and red blood cell count, blood electrolytes, and blood pH value. In case of infectious blood pictures, white blood cell count and neutrophil count increase; in case of blood loss or anemia, hemoglobin concentration and red blood cell count decrease; when there are abnormal conditions, attention should be paid to whether there is hypoxemia and hyperphosphatemia, etc.

　　6. Chest X-ray

　　Check for any abnormalities in the respiratory system and understand the child's lung condition.

　　Premature infants in the second week have significantly improved their ability to live. For premature infants with a higher birth weight, feeding will not be difficult. For premature infants with low birth weight and poor development, after treatment in the neonatal ward of the hospital, if the condition improves, they can be fed at home by the mother. If the child is hospitalized from birth, the mother can continue to express milk, and breastfeeding can start after discharge, and the problem is not too serious. If the mother's milk is already very little or almost none, it will be more difficult to start breastfeeding.

　　For premature infants aged 7 to 14 days, the energy supply should be calculated at 100 Kcal/kg (per kilogram of body weight) per day. A simple method can also be used: for each day of age, increase 10 milliliters of diluted milk per kilogram of body weight. When the child is 7 days old, the diluted milk volume per kilogram of body weight is 170 milliliters, and it increases to 180 milliliters on the 8th day, 190 milliliters on the 9th day, and 200 milliliters on the 10th day. For more than 10 days, the increase should be based on the child's actual body weight.

　　Premature infants aged 15 to 28 days should have their energy supply calculated at 120-140 kcal/(kg body weight) per day. Alternatively, a simple method can be used: take 1/5 of the child's current body weight as the total volume of diluted milk for each day. For example, if a child weighs 2.5 kg, the total milk volume for one day is 500 grams, which is equivalent to 500 milliliters. During this period, premature infants should still be fed with diluted milk, but the concentration of the milk can gradually increase from a 2:1 milk mixture to a 3:1 milk mixture (3 parts milk to 1 part water), and then gradually increase to a 4:1 milk mixture (4 parts milk to 1 part water).

　　When artificial feeding premature infants, milk should also be disinfected, sugared, and diluted, and the disinfection of feeding utensils should be especially noted. When increasing the amount of milk, refer to the feeding method of premature infants in the first week.

　　Premature infants must be kept warm at birth, and the actions should be gentle and quick. Coldness often causes irreversible complications, and the temperature in the delivery room must be maintained at about 25℃. To prevent asphyxia, it is best not to use anesthetics or sedatives that affect the fetal respiratory center during labor. When the fetal head is delivered, first squeeze out the mucus from the baby's mouth and nose. If it is not completely cleared, it can be suctioned out with a disinfected tube when the baby is completely delivered. Do not use gauze to wipe the mouth to avoid injury to the mucosa and promote infection. Oxygen should be given to those with respiratory distress or cyanosis. After the umbilical cord is cut, use a gauze pad soaked in disinfected vegetable oil to gently wipe away excessive vernix caseosa from the folds under the neck, armpits, and inguinal area, and then wrap it with cloth. Use 0.25% chloramphenicol or 0.5% neomycin eye drops to prevent conjunctivitis. After the preparation is complete, transfer the baby to an incubator that has been adjusted to the right temperature as soon as possible.

　　Premature infants should be kept quiet for the first 4 hours after entering the room, with the head turned to one side to allow mucus in the mouth to flow out. After that, change the position lightly every 2 to 3 hours. Take the temperature once every 4 hours, and the difference between the highest and lowest temperature should not exceed 1℃. If the temperature has stabilized between 36℃ and 37℃ for more than 3 times, it can be changed to once in the morning and once in the afternoon. If the temperature is higher than 37℃ or lower than 36℃, it still needs to be measured every 4 hours.

　　The use of oxygen is limited to those with respiratory distress or cyanosis and poor condition, and oxygen inhalation should not be taken as routine. Generally, oxygen inhalation can be stopped after a few hours when cyanosis disappears and respiration returns to normal. It is禁忌 over-oxygenation, excessive concentration, and prolonged time to avoid damaging the baby's eyes and lungs. Infants who are prone to cyanosis during feeding can be given a few minutes of oxygen inhalation before and after feeding.