Can asthma get worse during pregnancy? 

Pregnancy is a period of significant physiological change, and for those living with asthma, these changes can directly impact respiratory health. While many find their asthma remains stable or even improves during pregnancy, a substantial number find that their symptoms become more frequent or severe. Maintaining tight control over your asthma is not only vital for your own comfort but is essential for ensuring your baby receives a steady supply of oxygen throughout development. This article explores why asthma symptoms might escalate during pregnancy, how to identify worsening control, and the clinical steps necessary to protect both mother and child according to UK health standards. 

What We’ll Discuss in This Article 

• The statistical likelihood of asthma symptoms changing during pregnancy. 

• Why hormonal shifts can lead to increased airway sensitivity. 

• The physical impact of a growing baby on lung capacity. 

• Identifying early warning signs of declining asthma control. 

• The safety and importance of continuing asthma medication. 

• Clinical guidance for managing flare ups during each trimester. 

Can asthma attacks increase in frequency or severity while pregnant? 

Asthma can get worse during pregnancy, particularly during the second and third trimesters. Clinical observations in the UK suggest a rule of thirds: approximately one third of pregnant women will see an improvement in their asthma, one third will experience no change, and one third will find their symptoms worsen. For those whose asthma does deteriorate, the peak of this worsening often occurs between weeks 24 and 36 of the pregnancy. 

Worsening asthma during pregnancy is often linked to the baseline control of the condition before conception. Those with more severe asthma are statistically more likely to experience an escalation in symptoms. However, with consistent use of preventer medication and regular reviews with a midwife or GP, even worsening asthma can be managed effectively to ensure a safe delivery and a healthy baby. 

• Symptoms often return to their pre pregnancy state shortly after birth. 

• Flare ups are most common in the late second and early third trimesters. 

• Well controlled asthma is the best way to prevent pregnancy complications. 

• Most women do not experience significant asthma symptoms during labour itself. 

How pregnancy impacts your respiratory system 

Pregnancy impacts the respiratory system through a combination of hormonal and physical shifts. Progesterone levels rise significantly, which can cause you to breathe more often and feel more breathless, a sensation often referred to as air hunger. Additionally, increased oestrogen can cause the blood vessels in the lining of the nose and airways to swell, leading to congestion and making the lungs feel more sensitive to everyday triggers. 

Physical changes also play a role as the pregnancy progresses. The growing uterus pushes upwards against the diaphragm; the main muscle used for breathing. This reduces the functional residual capacity of the lungs, meaning there is less reserve air. For a person with asthma, this physical restriction can make a minor flare up feel much more severe because the lungs already have less space to expand. 

• Hormonal Sensitivity: Oestrogen and progesterone affect how the brain regulates breathing. 

• Diaphragm Elevation: The baby’s growth limits the downward movement of the breathing muscles. 

• Increased Oxygen Demand: Your body requires significantly more oxygen to support the foetus. 

Causes of worsening asthma symptoms 

The primary cause of worsening asthma during pregnancy is the underlying inflammation in the airways becoming more reactive to triggers. This can be exacerbated by pregnancy rhinitis, where the nasal passages become swollen and produce more mucus, leading to postnasal drip that irritates the lungs. If you are already prone to allergic asthma, these changes can make you more reactive to dander, dust, or pollen. 

Another common cause of worsening symptoms is the anxiety gap, where patients mistakenly stop taking their preventer medication out of fear that it might harm the baby. In reality, the inflammation caused by untreated asthma is far more dangerous to the baby’s oxygen supply than the medication. Consistent use of inhaled corticosteroids is the clinical gold standard for preventing the escalation of symptoms during pregnancy. 

• Pregnancy Rhinitis: Swollen nasal passages can trigger a persistent cough. 

• Gastro oesophageal Reflux (GERD): Heartburn, common in pregnancy, can irritate the airways. 

• Medication Non-compliance: Stopping preventers leads to rapid loss of control. 

Triggers and environmental factors 

During pregnancy, you may find that triggers you previously tolerated now cause a significant reaction. Common environmental triggers include cold air, traffic pollution, and strong smells. Because your body is already under increased respiratory demand, your threshold for a trigger induced flare up may be lower than it was before you were pregnant. 

It is particularly important to monitor indoor air quality. Spending more time at home preparing for the baby can increase exposure to household dust or cleaning chemicals. Ensuring your home is well ventilated and free from damp or mould is essential. If you have pets, you may need to be more rigorous with cleaning routines to reduce the dander levels that could aggravate your sensitive airways. 

• Household Irritants: Strong perfumes, cleaning sprays, and incense. 

• Weather Changes: Cold, dry air can cause immediate bronchoconstriction. 

• Viral Infections: Colds and flu are major causes of worsening asthma in pregnancy. 

Differentiating between normal breathlessness and worsening asthma 

It is vital to distinguish between the normal shortness of breath that comes with pregnancy and a genuine worsening of asthma. Normal pregnancy breathlessness typically occurs during exertion and is not accompanied by pain or wheezing. You might feel like you cannot take a deep enough breath, but your breathing remains quiet and your chest feels clear. 

In contrast, worsening asthma is characterised by a noisy wheeze when you breathe out, a persistent dry cough (especially at night), and a physical feeling of tightness or squeezing in the chest. If you find that you are needing your reliever inhaler (blue) more than two or three times a week, or if your symptoms are waking you up at night, your asthma is likely worsening and needs clinical review. 

Feature	Normal Pregnancy Breathlessness	Worsening Asthma Symptoms
Wheezing	Absent	Common whistling sound on exhale
Cough	Rare	Persistent, dry, and often nocturnal
Chest Sensation	Feeling of work or effort	Tightness or band around the chest
Peak Flow	Usually remains stable	Often shows a significant drop

Conclusion 

Asthma can get worse during pregnancy for about one third of women, primarily due to hormonal changes and physical pressure on the lungs. However, with proactive management and the consistent use of prescribed medications, these changes can be managed safely. Maintaining open communication with your midwife and GP ensures that your treatment plan is adjusted to your changing needs, protecting both your health and the health of your baby. 

If you experience severe, sudden, or worsening symptoms, call 999 immediately. 

Authority Snapshot 

This article was written by Dr. Stefan Petrov, a UK-trained physician with an MBBS and postgraduate certifications including BLS, ACLS, and PLAB 1 & 2. Dr. Petrov has extensive clinical experience in general medicine, surgery, and emergency care across UK hospital wards and intensive care units. He is dedicated to creating patient-focused health content that adheres to the latest NHS and NICE standards, ensuring accuracy and safety for those managing asthma during pregnancy.