Pregnancy complicated by pneumonia

　　(I) Etiology

　　Bacteria, viruses, fungi, and protozoa can all cause pneumonia. More than 50% of acute pneumonia is caused by Streptococcus pneumoniae infection, followed by viral infection. In addition, psittacosis mycoplasma, Mycoplasma pneumoniae, Chlamydia pneumoniae, legionella, and other pathogens can also cause pneumonia. The most common types of pneumonia in pregnancy complicated by pneumonia are pneumococcal pneumonia and varicella-zoster virus pneumonia. The main way of pathogen invasion is through aspiration of respiratory tract colonization bacteria with secretions, or through inhalation of pathogen-containing aerosols to cause direct implantation. The spread of infection from adjacent sites or from other sites through hematogenous dissemination is rare.

　　(II) Pathogenesis

　　During pregnancy, the immune function is reduced. After pregnancy, affected by pregnancy hormones, the respiratory tract mucosa becomes congested, edematous, and thickened, with increased respiratory tract secretions, which is unfavorable for the local defense mechanism of the respiratory tract. Pregnancy complicated by anemia, asthma, tuberculosis, pregnancy-induced hypertension, smoking, drug abuse, and HIV infection are prone to cause pulmonary infection.

　　It is generally believed that the impact of pregnancy complicated by pneumonia on pregnant women is greater than that of pneumonia during non-pregnancy on the patient themselves. The mortality rate of pregnant women with pneumonia is 0% to 4%. Yost reported that in 133 cases of pregnancy complicated by pneumonia, no pregnant woman died. The mortality rate is related to the severity of the illness and whether reasonable treatment is given. Due to the unique physiological state of pregnancy, some complications of pneumonia during pregnancy are significantly increased compared to non-pregnancy, such as the incidence of artificial mechanical ventilation, empyema, pneumothorax, cardiac tamponade, and atrial fibrillation. Similarly, the occurrence of these complications is also closely related to the timing of the patient's visit.

　　The impact of pregnancy complicated by pneumonia on the fetus depends on the severity of the pneumonia. Generally, the incidence of preterm birth in pregnant women with pneumonia is 4% to 44%. Madinger reported that in 6 cases of pregnancy complicated by pneumonia, 5 cases resulted in preterm birth. Berkowitz reported that the newborn weight of pregnant women with pneumonia was 400g less than that of the control group, the fetal intrauterine mortality rate was 2.6%, while Madinger reported a fetal intrauterine mortality rate of 12%.

　　3. Does pregnancy increase the risk of pneumonia? The physiological changes in the respiratory system during pregnancy make pregnant women more susceptible to pneumonia. Due to a series of changes in maternal immune function, such as a decrease in proliferative response of lymphocytes in the middle and late pregnancy, a decrease in the activity of natural killer cells, and a decrease in the number of helper T lymphocytes. Additionally, it has been found that trophoblasts can produce an immunosuppressive substance that reduces the maternal ability to recognize fetal tissue compatibility antigens. These physiological changes in immune function are of great significance for the growth of the fetus in utero and the maintenance of pregnancy. However, this decrease in cell-mediated immune function also reduces the maternal immune response to exogenous pathogens, making pregnant women more susceptible to infectious diseases caused by a low level of cellular immune function, such as pneumonia. Particularly, viruses and fungi are more likely to invade the body and cause disease during pregnancy. Furthermore, as the gestational age increases, the uterus gradually enlarges, raising the diaphragm by more than 4 cm. The transverse diameter of the thorax increases by 2-4 cm, and the circumference of the thorax increases by 5-7 cm. These physiological changes make it difficult for respiratory secretions in pregnant women to be completely cleared, leading to increased airway obstruction and thus increasing the incidence of pulmonary infection. The elevation of the diaphragm reduces functional residual capacity, increasing oxygen consumption by 20%, which reduces the tolerance of pregnant women to hypoxia, and this is more pronounced in the later stages of pregnancy.

　　Pneumonia during pregnancy is often more severe and may progress to sepsis or septicemia. It can cause toxic shock due to endotoxins, leading to multiple organ failure (MSOF) such as shock, disseminated intravascular coagulation, adult respiratory distress syndrome, heart failure, and renal failure, with severe consequences that may result in death. The impact on perinatal infants may include fetal death, preterm birth, low birth weight, and intrauterine infection (especially viral pneumonia).

　　The main symptoms include low-grade fever, cyanosis, chills, dyspnea, reduced breath sounds, coma, myalgia, expectoration of frothy mucous sputum, cough, and mucopurulent sputum.
　　1. Lobar pneumonia

　　The incubation period is 1-2 days, with an acute onset. Approximately 50% of patients have prodromal symptoms of upper respiratory tract infection or precipitating factors such as exposure to cold or fatigue. Subsequently, symptoms such as fever, chills, cough, chest pain, expectoration of mucopurulent or rust-colored sputum may occur. In cases with widespread lesions, respiratory distress and cyanosis may appear. If not treated promptly, symptoms such as confusion, delirium, coma, and shock may occur. Sometimes, complications such as pleurisy and pericarditis may occur. The typical physical examination findings include tactile vocal fremitus, dullness on percussion, reduced breath sounds on auscultation, and the possibility of bronchial breath sounds. Pathogens commonly seen include Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli.

　　2. Lobular pneumonia

　　The lesion is located in the bronchioles, interstitial lung tissue, and alveoli, with clinical manifestations including fever, headache, myalgia, cough, expectoration of frothy or mucopurulent sputum, physical examination showing slightly dull percussion over the middle and lower lung fields, reduced breath sounds on auscultation, bronchial and alveolar sounds, and moist rales. Pathogens commonly seen include viruses, mycoplasma, and rickettsia.

　　3. Interstitial pneumonia

　　The lesion is located in the bronchial wall, the surrounding tissue of the bronchus, and the alveolar wall. The inflammation spreads along the interstitial lymphatic vessels, causing localized lymphangitis and lymphadenitis. The clinical manifestations are low fever, cough, myalgia, and mucoid sputum. The signs are not obvious, and the pathogens are mostly viruses such as measles and varicella-zoster virus.

　　1. General preventive measures for pneumonia

　　(1) Eat high-protein, high-calorie foods rich in vitamin C to enhance the body's resistance.

　　(2) Pay attention to keeping warm when the weather changes suddenly.

　　(3) During the epidemic period of viral or bacterial infections, try to minimize the visits to public places, avoid and reduce contact with infected populations; in addition, avoid contact with infected birds or domestic animals to prevent psittacosis pneumonia.

　　(4) Strengthen the hygiene management of the water supply system, humidifier, sprayer, etc. of air conditioners to reduce the transmission of legionella pneumonia.

　　2. Specific preventive measures for pneumonia:
　　There has been great progress in the development and application of immune globulins and specific pneumonia vaccines during pregnancy, but most preventive effects still need to be investigated.

　　(1) Pneumococcal vaccine can be used to prevent pneumococcal pneumonia and can reduce the occurrence of drug-resistant pneumococci. It is recommended for pregnant women with sickle cell anemia to use this vaccine, but it is not advocated for normal healthy pregnant women.

　　(2) Influenza vaccine is derived from protein sources and is safe for pregnant women. It is recommended that all pregnant women in the middle and late stages of pregnancy be vaccinated with influenza vaccine to prevent influenza.

　　(3) If pregnant women come into contact with patients infected with varicella-zoster virus, they may be infected with varicella-zoster virus. Immune globulin against varicella-zoster virus should be administered within 96 hours after contact to prevent or alleviate the symptoms of varicella-zoster virus infection. The usual dose is 12.5U/kg intramuscular injection, but this passive immunization method is limited to patients with protective immune deficiency.

　　The main examinations include: pleural effusion examination, sputum culture, bacteriological examination of sputum and lower respiratory tract secretions, and chest plain film.
　　Pathogenic diagnosis:Mainly based on the examination and culture of respiratory tract secretions, sputum, blood, or pleural effusion, detection of specific antibodies, and PCR detection of specific pathogen DNA. At present, there is no method that is both sensitive and simple, and easy to promote, for the diagnosis of chlamydophila pneumoniae pneumonia.

　　Chest X-ray examination:Understanding the involved parts and severity of pneumonia is helpful for estimating the condition and pathogen. The X-ray manifestation of lobar pneumonia is dense, uniform shadow caused by pulmonary parenchymal lesions, and bronchial airway signs can be seen; the X-ray manifestation of bronchopneumonia is irregular, small patchy or dot-like shadow along the pulmonary texture distribution; the X-ray manifestation of interstitial pneumonia is fine, irregular, high-density cord-like shadows on one or both sides of the lower lungs, extending outward from the hilum, intertwining into a network, with disseminated small dot-like high-density shadows in the middle, and the hilar lymph nodes on both sides are enlarged with blurred edges. It is generally not advisable to perform X-ray examinations during pregnancy, and abdominal protection should be provided if necessary.

　　Pregnant women with pneumonia should eat (drink) more:
　　1. Fluids, especially juice;
　　2. Fresh fruits and vegetables;
　　3. Oily fish, eggs, and other foods rich in vitamin A.

　　1. Supportive therapy: bed rest, ensure nutrition, correct acidosis and water and electrolyte disorders, correct hypoxemia.

　　2. Treatment of the cause: the use of antibiotics is the main treatment method for bacterial and mycoplasma pneumonia. The use of medication based on bacterial culture and drug sensitivity test results is the most reasonable. Before the results of the drug sensitivity test come out, speculate on the pathogen based on clinical symptoms, signs, sputum smears, etc., and choose broad-spectrum antibiotics that have no obvious effect on the fetus. Streptococcus pneumoniae and Streptococcus are首选 penicillin and cephalosporins; Gram-negative bacilli can be selected for ampicillin (ampicillin), sulfoxamine (sulphamethoxazole); Anaerobic bacteria pneumonia can be selected for penicillin, erythromycin, carbenicillin (carbenicillin); Mycoplasma and chlamydia pneumonia are首选 erythromycin; Viral pneumonia can be treated with antiviral drugs, such as 10mg rimantadine for influenza A virus, once every 12 hours, herpes virus can be treated with acyclovir (acyclovir) 5mg/(kg·d), taken every 8 hours.

　　3. Improve the patency of the respiratory tract and remove sputum in a timely manner.

　　4. Monitor whether the fetus is hypoxic and whether there is intrauterine infection.

　　5. Obstetric management

　　(1) In the early stages of pregnancy, to avoid adverse effects on the fetus caused by high fever, etc., induced abortion can be performed after the pneumonia is cured. However, if the fetus is precious, it can also continue the pregnancy.

　　(2) Mild pneumonia can be actively treated and wait for the fetus to mature for delivery. Severe pneumonia should correct respiratory failure, hypoxemia, acidosis, and electrolyte imbalance. The timing and method of termination of pregnancy should be decided based on the gestational age, intrauterine condition of the fetus, and the presence of obstetric complications. Vaginal delivery is preferred for those without indications for obstetric surgery. Close monitoring, oxygen therapy, and prevention of intrauterine hypoxia in the fetus should be carried out during labor to shorten the second stage of labor, assist with forceps delivery, and prevent postpartum hemorrhage and infection.