Introduction
The respiratory system can experience various anatomic and physiologic changes during a normal pregnancy. Sometimes, these changes may lead to the development of several acute pulmonary disorders in the patient like aspiration, thromboembolic disease, pulmonary edema, and amniotic fluid embolism. Pregnancy can also cause changes in the progress of some chronic pulmonary diseases such as asthma and sarcoidosis. Also, in converse, if these pulmonary conditions are poorly controlled, they can adversely affect pregnancy.
How Does Pregnancy Affect Thoracic Cage Anatomy?
Hormonal changes are seen during pregnancy which can affect the upper respiratory tract and upper airway mucosa, leading to hyperemia, mucosal edema, an increase in the friability of the mucosa, and increased secretion. Estrogen causes tissue edema, capillary congestion, and an increase in the size of cells associated with mucous glands. The uterus enlargement, along with hormonal changes, causes variation in the anatomy of the thoracic cage. The function of the diaphragm remains normal.
Does Pregnancy Affect Pulmonary Function?
Anatomical changes seen in the thorax cause a progressive decrease in functional residual capacity by 10 % to 20 %. The residual volume has a possibility to decrease slightly during pregnancy but is not consistently found. The decreased expiratory reserve volume has definite changes. Hormonal changes do not significantly cause any effect on airway function.
What Are Pregnancy-Related Disorders That Affect the Respiratory System?
1. Amniotic Fluid Embolism -
Amniotic fluid embolism is rare (1 case per 8000 to 80,000 births) but still can prove to be a potentially catastrophic complication and has a mortality rate of 10 % to 80 %. This is commonly seen to occur with labor and delivery but can be associated with uterine manipulation, uterine trauma, and the early postpartum period. This can finally lead to pulmonary hypertension, and acute left ventricular failure might occur.
Clinically, it usually involves a sudden onset of severe dyspnea, hypoxemia, and cardiovascular collapse. Less commonly seen symptoms are hemorrhage caused by disseminated intravascular coagulation and fetal distress. The diagnosis is usually made depending on clinical examination, fetal squamous cells in a wedged pulmonary capillary aspirate. The treatment involves routine resuscitative and supportive measures with the provision of adequate oxygenation, ventilation, and inotropic support. No specific therapy has been proven to be effective, although corticosteroids have been suggested. The survivors can develop complications like disseminated intravascular coagulation, acute respiratory distress syndrome (ARDS), or both.
2. Tocolytic Pulmonary Edema
Beta-adrenergic agonists, particularly Ritodrine and Terbutaline that are used to inhibit uterine contractions and preterm labor, might cause pulmonary edema during pregnancy. The frequency ranges from 0.3 % to 9 %. The clinical presentation is similar to acute respiratory distress with features of pulmonary edema. The diagnosis is clinical. The treatment involves discontinuation of beta-agonist therapy. The additional treatment is supportive, which includes diuresis.
3. Preeclampsia and Pulmonary Edema
Pulmonary edema associated with preeclampsia is rare. It clinically presents as acute respiratory distress in a patient with preeclampsia. Preeclampsia shows symptoms of hypertension, proteinuria, and peripheral edema, seen usually in the third trimester. The standard approach is to restrict fluid and administration of supplemental oxygen and diuresis. Invasive monitoring might be useful in case inotropic vasodilator therapy becomes necessary.
4. Peripartum Cardiomyopathy
Cardiogenic pulmonary edema is important to be considered in the differential diagnosis of acute respiratory failure in pregnancy. Cardiac failure can be seen even in the absence of preexisting heart disease due to hypertensive disease of pregnancy and peripartum cardiomyopathy. This condition is idiopathic and presents during the last month of pregnancy or the postpartum period and can be associated with significant mortality. Tachycardia and increased cardiac output during labor and early postpartum can precipitate pulmonary edema.
5. Gestation Trophoblastic Disease
Pulmonary hypertension and pulmonary edema can cause complications of benign hydatidiform pregnancy due to trophoblastic pulmonary embolism (PE). A molar pregnancy can have an association with the development of choriocarcinoma, which commonly causes multiple discrete pulmonary metastases and occasional pleural effusions.
6. Asthma and Pregnancy
Asthma during pregnancy has a variable course. One-third of patients show improvement, one-third remain stable, and one-third show worsening of the condition. Gestational weeks 24 to 36 seem to be the most difficult in patients with symptomatic asthma. The clinical features of asthma during pregnancy are similar to that of non-pregnant patients. Pulmonary function tests can be used to check the presence of airflow obstruction. The management includes avoiding and controlling the triggers of asthma. Acute exacerbations that require emergency management typically require a course of systemic corticosteroids. Oxygen can be used liberally. A beta-agonist with or without Ipratropium can be given, and Theophylline has limited use in such situations of acute exacerbations. Aggressive management of the exacerbation of asthma is necessary because of the greater risk to the fetus from untreated asthma.
What Are the Pulmonary Infections in Pregnancy?
1. Pneumonia
Pneumonia is an uncommon yet serious complication seen during pregnancy and is the most frequent cause of nonobstetric infection and the third most frequent cause of indirect obstetric death.
2. Bacterial, Viral, and Fungal Infections
Streptococcus pneumoniae is the most common pathogen causing pneumonia during pregnancy. Other agents that can be associated are Mycoplasma pneumoniae, Haemophilus influenzae, and Legionella species. Influenza and other viruses can also lead to pneumonia. Bacterial pneumonia needs antibiotic management, and safe antibiotics during pregnancy are Penicillins, Cephalosporins, and Macrolides.
3. Tuberculosis
Many pregnant patients require screening for tuberculosis infection, and some require preventive therapy before going for delivery. Active tuberculosis in pregnancy needs aggressive investigation and must always be treated. HIV (human immunodeficiency virus) infection and drug-resistant tuberculosis are special challenges in pregnancy. Tuberculosis in pregnancy is commonly managed with Isoniazid and Rifampin. Ethambutol can be added during the initial therapy phases until sensitivities are available.
What Are Other Pulmonary Disorders That Develop During Pregnancy?
1. Acute Respiratory Distress Syndrome
Obstetric complications and nonobstetric conditions both can cause ARDS in a pregnant patient.
2. Pleural Diseases
Pleural effusions can be associated with obstetric complications such as preeclampsia, but some patients may remain asymptomatic.
3. Interstitial Lung Disease
Most interstitial lung diseases are not usually associated with pregnancy, but they might reduce arterial oxygen saturation due to the defect in the gas transfer.
4. Cystic Fibrosis
Medical advances in the management of patients suffering from cystic fibrosis have extended life expectancy into childbearing age, but fertility might be a problem sometimes. Hence, contraception and planned pregnancy are important while treating these patients.
5. Pulmonary Vascular Disease
Pregnancy in patients suffering from pulmonary hypertension can have an extremely high mortality risk.
6. Obstructive Sleep Apnea
If the pregnancy is complicated by obstructive sleep apnea, it can lead to potential adverse effects for both the mother and the fetus.
Conclusion
There are various normal and abnormal changes seen in the respiratory tract during pregnancy. It has now become easier to consult your physician at the ease of home. Hence, when in doubt or require detailed information, consult a specialist.
