Introduction:

Asthma is a common condition affecting approximately 8% of pregnant women. Epidemiological evidence demonstrates that the course of asthma during pregnancy is variable and unpredictable, with approximately one-third of women experiencing an improvement, one-third experiencing a worsening, and one-third having no changes in asthma symptoms. It is also apparent that poor control of maternal asthma leads to increased risk of adverse maternal and fetal outcomes. Because of these risks and the unpredictable course of asthma symptoms, it is especially important to provide appropriate monitoring and management of the asthmatic patient throughout pregnancy.

Clinical Course:

Women with well-controlled asthma usually have good pregnancy outcomes. Pregnancy in women with more severe asthma can precipitate worsening control and lead to increase in maternal and neonatal morbidity.

Clinical Features:

Symptoms
Breathlessness, cough, wheeze, chest tightness and nocturnal waking due to cough.

Signs
Raised respiratory rate, wheeze, use of accessory muscles and tachycardia.

Triggering Factors
Pollen, animal fur, dust, exercise, cold, emotion, upper respiratory infections and medications (aspirin and beta blockers).

History and Physical:

Symptoms of asthma peak in the late second or early third trimester, but exacerbations are rare during labor and the peripartum period.

Physical examination in people with bronchial asthma may be normal, but the most frequent physical sign is wheezing on auscultation. Wheezing may be absent in cases of severe bronchial asthma exacerbations as a result of severe reduction of airflow (silent chest).

Pathophysiology:

Given below are a number of changes that happen during pregnancy that have an effect on bronchial asthma.

• In pregnant women, metabolic rate increases by 15%. This causes a 20% rise in the oxygen required and a 30% – 40% rise in minute ventilation. This increased ventilation results in respiratory alkalosis which is a condition in which the arterial partial pressure of carbon dioxide and bicarbonate drops and the pH rises.
• The uterus grows in size and impinges on the diaphragm. As a result, the functional residual capacity goes down.
• The changes in the mother’s immune mechanism are linked to the change from T-helper 1-type cytokine to Th2-type which is necessary for the well-being of the fetus. The Th2 uprise can worsen bronchial asthma in pregnant women.
• Around 20% of pregnant women experience rhinosinusitis as a result of mucosal and laryngeal inflammation caused by the estrogen hormone.

Monitoring:

• Review every four to six weeks throughout pregnancy to monitor asthma control and detect and treat any changes in respiratory function.
• Women with very poorly controlled asthma should be seen every 1 – 2 weeks until control is achieved.
• Spirometry should be performed at regular visits to monitor lung function. Between visits, women can monitor their lung function using a peak flow meter, if required.
• Discuss and agree on an asthma action plan to be followed if the woman’s asthma deteriorates.
• Women should be advised to report any reduction in fetal activity.
• In women with sub-optimally controlled asthma, consider regular fetal ultrasound check-up from 32 weeks’ gestation. If a severe exacerbation occurs, arrange a follow-up ultrasound.
• Consider a chest X-ray in the presence of respiratory compromise if respiratory complications are suspected following examination (very small fetal risk is far outweighed by the potential benefits for both the mother and fetus).

Breastfeeding:

The quantity of asthma medicines that get into breast milk is very little. According to the NAEPP, prednisone, theophylline, antihistamines, ICSs, beta agonists and cromolyn can be taken by women breastfeeding their children. Women should be made aware that the medicines should be kept to the minimum necessary for control. Taking the medicines after breastfeeding is advised.

Prognosis:

Uncontrolled asthma in pregnancy has been linked with a higher incidence of low fetal birth weight and preterm birth. However, in general, the prognosis of asthma in pregnancy is similar to that of asthma in other populations. Patients who are pregnant and diagnosed with bronchial asthma should receive adequate asthma assessment and treatment. Bronchial asthma should be treated and managed in pregnant women the same way as in non-pregnant patients.

Complications of Uncontrolled Asthma:

Associated with Maternal

• Pregnancy-induced hypertension
• Pre-eclampsia
• Hyperemesis
• Vaginal haemorrhage
• Complicated labour

Fetal

• Intrauterine growth restriction
• Low birth weight
• Preterm birth
• Increased perinatal mortality
• Neonatal hypoxia

Conclusion:

Pregnant women should be made to understand that having asthma under control is essential for the well-being of the fetus. It is necessary for the patients to have some basic knowledge about asthma. They should know the proper use of controller and rescue medications and should be able to identify what sets off the condition. They should be able to monitor themselves and should also have regular consults with a clinician to make sure asthma is under control.

Dr. Anantha Subramanian
Consultant Pulmonologist
Kauvery Hospital