Pregnancy induces profound anatomical and physiological alterations in the maternal respiratory tract to meet the increasing metabolic demands of the fetoplactental unit. Driven largely by the hormone progesterone, the respiratory center in the brainstem experiences increased sensitivity to carbon dioxide, which stimulates a higher respiratory drive.
These adjustments lead to a state of mild chronic compensated respiratory alkalosis. The mother hyperventilates slightly to maintain a lower arterial carbon dioxide level, facilitating the diffusion of carbon dioxide away from the fetus. A common clinical observation in midwifery practice is that pregnant women frequently report a subjective sensation of breathlessness, or physiological dyspnea, even in the absence of any underlying cardiorespiratory pathology.
Asthma is one of the most common chronic medical conditions affecting pregnant women. Its clinical course during pregnancy is notoriously unpredictable: roughly one-third of women experience an improvement in symptoms, one-third remain unchanged, and one-third experience a worsening of their condition. Poorly controlled asthma poses severe risks, including maternal hypoxia, preeclampsia, intrauterine growth restriction, and preterm birth.
Management focuses on maintaining adequate control through regular peak flow monitoring and appropriate pharmacotherapy. Most standard asthma medications, including inhaled corticosteroids and short-acting beta-agonists like albuterol, are safe to use during pregnancy. Uncontrolled asthma is far more dangerous to the developing fetus than the medications used to treat it. Midwives must reinforce medication adherence, as many women stop using their inhalers out of fear of harming the baby.
Pneumonia remains the most common serious non-obstetric infection complicating pregnancy. The physiological immunosuppression of pregnancy, combined with upward displacement of the diaphragm and reduced functional residual capacity, leaves pregnant women more vulnerable to severe respiratory infections and rapid clinical deterioration.
Typical pathogens include Streptococcus pneumoniae and atypical agents like Mycoplasma. Viral pneumonias, such as influenza, also carry high morbidity. Symptoms include cough, fever, pleuritic chest pain, and dyspnea. Initial assessment requires prompt auscultation, pulse oximetry, and chest radiography with abdominal shielding if pulmonary consolidation is suspected. Treatment involves prompt administration of pregnancy-safe antibiotics, aggressive hydration, and oxygen therapy to maintain maternal oxygen saturation above 95 percent, thereby preventing fetal distress.
The fetus has no independent source of oxygen and relies entirely on a continuous supply from the intervillous space of the placenta. When maternal respiratory disease leads to hypoxia, the oxygen gradient across the placenta is compromised. Acute maternal hypoxemia rapidly results in fetal hypoxemia, leading to redistribution of fetal cardiac output away from peripheral organs and toward the brain, heart, and adrenals. This redistribution triggers late decelerations on fetal heart rate monitors, reduced fetal movements, and, if prolonged, metabolic acidosis, anoxic brain injury, or fetal demise.
Managing acute respiratory compromise in pregnancy requires a multidisciplinary approach involving midwives, obstetricians, and pulmonologists. Immediate stabilization focuses on airway, breathing, and circulation. Supplemental oxygen should be applied promptly via nasal cannula or face mask to keep oxygen saturations above 95 percent.
Midwifery surveillance plays a frontline role in detecting early signs of respiratory failure.
Positioning the patient in a semi-Fowler's or left lateral tilt position helps relieve inferior vena cava compression while maximizing lung expansion.