Lung Health During Pregnancy: What Every Expecting Mother in Pakistan Must Know
Pregnancy changes every system in the body — including the lungs and airways. A pulmonologist explains why breathlessness during pregnancy is not always normal, which respiratory conditions require specialist care, which medications are safe, and how to protect both mother and baby throughout every trimester.
Pregnancy is one of the most profound physiological transformations the human body undergoes. In the space of nine months, nearly every organ system adapts to support a growing life — and the respiratory system is no exception. The lungs work harder, the airways become more sensitive, breathing mechanics change as the uterus expands, and the immune modulation of pregnancy alters the way the body responds to infections and allergens.
For most healthy women, these changes are manageable and well tolerated. But for women with pre-existing respiratory conditions — asthma, allergic rhinitis, sleep apnea — pregnancy can bring significant challenges that require specialist input. And for women without a prior lung diagnosis, pregnancy can sometimes unmask conditions that were previously subclinical or reveal new respiratory problems that develop for the first time during gestation.
As a pulmonologist, I am consulted regularly by obstetricians and by pregnant women themselves — women who are breathless, worried about their asthma medications, concerned about a cough that will not clear, or anxious about whether an air quality warning means they should stay indoors. This article addresses all of those concerns directly. Because respiratory health during pregnancy is not just a matter of comfort — it directly affects fetal growth, oxygen delivery to the baby, and the outcomes of both mother and child.
How Pregnancy Changes the Respiratory System
Understanding the normal physiological changes of pregnancy in the respiratory system is essential for distinguishing what is expected from what requires medical attention.
Increased Oxygen Demand
Pregnancy increases the body's overall metabolic rate and oxygen consumption by approximately 20 percent. The growing fetus, placenta, and uterus all require continuous oxygen delivery. The maternal heart and lungs must increase their output to meet this demand — the heart rate rises, cardiac output increases, and the respiratory system must deliver more oxygen per minute to the bloodstream. This increased respiratory demand is one of the primary reasons breathlessness is so common in pregnancy.
Elevated Progesterone and Its Effects on Breathing
Progesterone — which rises dramatically throughout pregnancy — is a potent respiratory stimulant. It acts directly on the brainstem's respiratory control centres, increasing the sensitivity of the breathing reflex and causing deeper, slightly more rapid breathing. This progesterone-driven hyperventilation lowers the arterial carbon dioxide level — a state called respiratory alkalosis — which is entirely normal in pregnancy but contributes to the subjective feeling of breathlessness and air hunger that many pregnant women experience, particularly in the first and second trimesters.
Mechanical Compression by the Growing Uterus
As pregnancy progresses — particularly in the second and third trimesters — the enlarging uterus pushes upward against the diaphragm, elevating it by approximately four centimetres. This reduces the resting position of the diaphragm and decreases the functional residual capacity — the amount of air remaining in the lungs after a normal exhalation. The lungs have less reserve volume available, making breathing feel more effortful, particularly when lying flat or bending forward. The thoracic cage compensates by flaring outward — the subcostal angle widens by approximately 35 degrees — but this compensation is only partially effective.
Airway Changes
Increased blood flow and hormonal changes during pregnancy cause congestion and swelling of the nasal and upper airway mucosa — the same mechanism responsible for the common complaint of nasal congestion in pregnancy. This upper airway swelling increases nasal resistance, promotes mouth breathing, and in susceptible women can worsen or trigger snoring and obstructive sleep apnea. The lower airways are also affected: progesterone causes smooth muscle relaxation that slightly widens the bronchi, while oestrogen increases mucus secretion and the inflammatory response of the airway lining.
Blood Volume and Oxygen Carrying Capacity
Blood volume increases by approximately 40 to 50 percent during pregnancy, primarily through expansion of plasma volume. Red cell mass also increases, but proportionally less — producing a physiological "dilutional anaemia" of pregnancy. The relatively lower haemoglobin concentration means that each unit of blood carries slightly less oxygen, compensated by increased cardiac output and respiratory rate. Women with significant iron deficiency anaemia — common in Pakistan — have reduced oxygen-carrying capacity that can substantially worsen breathlessness beyond the normal physiological level.
Normal Versus Abnormal Breathlessness in Pregnancy
Up to 70 percent of pregnant women experience breathlessness at some point during pregnancy — most commonly in the first trimester (driven by progesterone) and in the third trimester (driven by mechanical compression). This physiological breathlessness has characteristic features that distinguish it from breathlessness due to a pathological cause.
Physiological breathlessness of pregnancy is typically mild, comes on gradually, is most noticeable at rest or with mild exertion, does not wake the woman from sleep, is not associated with wheeze, chest pain, or cough, and does not progressively worsen over days or weeks. It is the subjective sensation of needing to breathe more deeply — a mild air hunger — rather than a struggle to breathe.
Breathlessness that should be medically evaluated includes any breathlessness that is severe, that comes on suddenly, that wakes the woman from sleep, that is associated with wheeze or chest tightness, that is accompanied by chest pain or palpitations, that is rapidly progressive, or that is accompanied by a cough with blood or purulent sputum. These features suggest a pathological cause that requires specific investigation and management.
Asthma in Pregnancy — The Most Important Respiratory Condition
Asthma affects approximately 8 percent of pregnant women — making it the most common serious medical condition complicating pregnancy. The interaction between asthma and pregnancy is bidirectional: pregnancy affects asthma control, and poorly controlled asthma affects pregnancy outcomes.
How Does Pregnancy Affect Asthma?
The effect of pregnancy on asthma follows the "rule of thirds": approximately one third of women find their asthma improves during pregnancy, one third find it stays the same, and one third find it worsens. Worsening is most common in the second trimester and typically improves in the final four weeks of pregnancy. The mechanisms are complex — progesterone's bronchodilating effect may improve control in some women, while oestrogen's pro-inflammatory effects worsen airway hypersensitivity in others. Viral respiratory infections — which are more common and more severe in pregnancy due to immune modulation — are the most frequent trigger for asthma exacerbations during gestation.
Why Good Asthma Control Matters During Pregnancy
Poorly controlled asthma during pregnancy is associated with a significantly increased risk of adverse maternal and fetal outcomes — including pre-eclampsia, gestational hypertension, preterm birth, low birth weight, and fetal growth restriction. These risks result from the episodic hypoxia (low blood oxygen) that occurs during asthma attacks, reducing oxygen delivery to the fetus, and from the systemic inflammatory state of uncontrolled asthma affecting placental function.
Well-controlled asthma, by contrast, is associated with pregnancy outcomes essentially equivalent to those of non-asthmatic women. The clinical message is clear: treating asthma aggressively during pregnancy produces better outcomes for both mother and baby than undertreating it out of fear of medication.
Are Asthma Medications Safe in Pregnancy?
This is the question I am asked most frequently by pregnant women with asthma — and the fear of harming their baby through medication is one of the most common reasons for poor asthma control during pregnancy. I want to address this directly and clearly.
Inhaled corticosteroids — the preventer medication that is the foundation of asthma management — are safe throughout pregnancy and should be continued without interruption. Multiple large studies have confirmed that inhaled corticosteroids at standard doses do not increase the risk of congenital abnormalities, preterm birth, or low birth weight. Budesonide has the most pregnancy safety data and is the preferred ICS during pregnancy, but other inhaled corticosteroids are also considered safe.
Short-acting bronchodilators — salbutamol (the blue reliever inhaler) — are also safe in pregnancy and should always be available for use during breathlessness or an asthma attack. The benefit of treating acute breathlessness and preventing hypoxia vastly outweighs any theoretical risk from the medication.
Long-acting bronchodilators (LABAs) such as salmeterol and formoterol — used in combination with ICS — are generally considered safe when needed for asthma control, though the ICS component should always be optimised first before adding a LABA in pregnancy.
What must be avoided is the mistaken belief that stopping or reducing inhaled medications during pregnancy protects the baby. Uncontrolled asthma with episodic hypoxia causes far more harm to the developing fetus than the medications used to prevent it.
Budesonide, fluticasone, beclometasone — all considered safe. Do not reduce or stop your preventer inhaler during pregnancy. Asthma exacerbations from undertreated disease are more dangerous than the medication itself.
The blue reliever inhaler is safe throughout pregnancy. Use it when needed for breathlessness, wheeze, or chest tightness. Never withhold it during an acute attack.
Leukotriene receptor antagonists such as montelukast are considered safe in pregnancy and may be continued if they were providing good asthma control before conception. Stopping them risks worsening control.
A short course of oral prednisolone for a severe asthma exacerbation is safe and necessary. The risk of undertreated severe asthma far exceeds the small risk of a brief steroid course. Long-term oral corticosteroids require specialist supervision.
Aspirin and ibuprofen trigger bronchoconstriction in approximately 10 percent of asthmatic patients. Avoid them during pregnancy if you have known aspirin-sensitive asthma. Paracetamol is the safe analgesic alternative.
The most dangerous decision for a pregnant woman with asthma is stopping her inhaled medication out of fear. Always discuss any medication concern with your pulmonologist before making changes — do not stop treatment unilaterally.
I see pregnant women every week who have stopped their asthma inhalers because they are afraid of harming their baby — and arrive in my clinic breathless, wheezing, and having had two attacks in the previous month. The medication did not harm the baby. The decision to stop the medication harmed both of them. Please — if you have asthma and you are pregnant, keep taking your inhalers. They are not a risk to your pregnancy. Uncontrolled asthma is.
— Dr. Nabila Zaheer, Pulmonologist
Other Respiratory Conditions During Pregnancy
Allergic Rhinitis in Pregnancy
Allergic rhinitis affects a significant proportion of pregnant women and can worsen during gestation due to hormonal effects on nasal vascularity. Pregnancy rhinitis — nasal congestion without allergic cause, driven purely by hormonal changes — affects up to 20 percent of pregnant women and resolves after delivery. Managing allergic rhinitis during pregnancy improves sleep quality, reduces the risk of sinusitis, and — in women with coexisting asthma — directly improves asthma control through the united airway mechanism.
Intranasal corticosteroid sprays — budesonide nasal spray in particular — are considered safe during pregnancy and are the most effective treatment for allergic rhinitis. Second-generation antihistamines such as loratadine and cetirizine are also considered safe in pregnancy. Nasal saline irrigation is completely safe and highly effective as an adjunct. Decongestants containing pseudoephedrine or phenylephrine should be avoided, particularly in the first trimester and during breastfeeding.
Sleep Apnea and Snoring in Pregnancy
Snoring occurs in approximately 25 percent of pregnant women — a dramatic increase from pre-pregnancy rates — due to upper airway oedema, weight gain, and nasal congestion. New-onset snoring in pregnancy is associated with increased risk of gestational hypertension, pre-eclampsia, and fetal growth restriction, independent of obesity. Obstructive sleep apnea — which occurs in approximately 10 to 20 percent of obese pregnant women — carries additional risks of gestational diabetes and adverse cardiovascular outcomes.
Pregnant women with pre-existing sleep apnea should continue CPAP therapy throughout pregnancy — safe for both mother and fetus, and particularly important because the hormonal and mechanical changes of pregnancy can worsen sleep-disordered breathing. Women who develop significant new snoring with gasping, witnessed apneas, or excessive daytime sleepiness during pregnancy should be referred for a sleep study and, if OSA is confirmed, offered CPAP therapy.
Pulmonary Embolism in Pregnancy
Pregnancy is a hypercoagulable state — the body increases clotting factor levels to reduce the risk of postpartum haemorrhage. This same hypercoagulability significantly increases the risk of deep vein thrombosis and pulmonary embolism, which is the leading cause of direct maternal mortality in many countries. The risk is highest in the third trimester and in the six weeks after delivery.
Any pregnant woman who develops sudden breathlessness, chest pain, or leg swelling — particularly unilateral leg swelling — should seek emergency evaluation for pulmonary embolism. The index of suspicion must be high, and investigation should not be delayed out of concerns about radiation from CT scanning. The risk to mother and fetus from an undiagnosed PE is far greater than the minimal radiation exposure from a CTPA performed with standard fetal shielding. Anticoagulation with low-molecular-weight heparin is the treatment — it does not cross the placenta and is safe for the fetus.
Pneumonia in Pregnancy
Pneumonia during pregnancy is associated with significantly higher maternal and fetal morbidity than in non-pregnant adults — including preterm labour, fetal distress, and maternal respiratory failure. The immune modulation of pregnancy makes women more susceptible to certain organisms, and the reduced functional residual capacity of the gravid lung leaves less physiological reserve to tolerate the hypoxia of pneumonia. Any pregnant woman with fever, cough, and breathlessness should receive prompt medical evaluation. Bacterial pneumonia is treated with antibiotics safe in pregnancy — amoxicillin and azithromycin being the most commonly used. Viral pneumonia from influenza can be particularly severe in pregnant women, which is the basis for the strong recommendation for annual influenza vaccination in all pregnant women.
Tuberculosis in Pregnancy
Pakistan's high TB burden makes TB in pregnancy a clinically important consideration. Active TB during pregnancy is associated with increased risk of preterm birth, low birth weight, and perinatal mortality — and untreated TB carries significant maternal mortality risk. First-line antituberculous therapy — isoniazid, rifampicin, ethambutol, and pyrazinamide — is safe during pregnancy, and treatment must not be delayed or withheld because of pregnancy. Pyridoxine (vitamin B6) supplementation is recommended alongside isoniazid to prevent peripheral neuropathy in the mother. Any pregnant woman with a cough lasting more than two weeks, weight loss, or night sweats should have TB specifically investigated.
Protecting Your Lungs and Your Baby's Lungs During Pregnancy
The ideal time to discuss respiratory health in pregnancy is before conception — when medications can be reviewed, optimised, and where necessary switched to pregnancy-safe alternatives in a planned, unhurried way. If you have asthma, allergic rhinitis, or any other respiratory condition and are planning a pregnancy, please discuss this with your pulmonologist at your earliest opportunity. If you are already pregnant and have a respiratory condition that has not been reviewed since conception, book an appointment urgently. Do not wait for a problem to arise.
The influenza vaccine is one of the most strongly recommended and most clearly evidence-supported interventions in pregnancy. Pregnant women are at significantly higher risk of severe influenza than non-pregnant adults, and influenza in pregnancy is associated with preterm birth, fetal growth restriction, and maternal ICU admission. The vaccine is safe at any stage of pregnancy, protects the mother throughout the remainder of the pregnancy, and — crucially — passes maternal antibodies to the newborn, providing protection during the first months of life before the baby can be vaccinated directly. It is recommended in every pregnancy, every year.
If you smoke and are pregnant, stopping is the single most important thing you can do for your baby's lung health and your own. Maternal smoking during pregnancy causes fetal growth restriction, increases the risk of preterm birth, and — most relevantly for long-term respiratory health — impairs fetal lung development, resulting in a child who is born with smaller, less well-developed airways and a significantly increased lifetime risk of asthma, respiratory infections, and COPD. Secondhand smoke exposure carries similar — though smaller — fetal lung risks. The home must be smoke-free throughout pregnancy and after the baby is born.
In Pakistan, pregnant women who cook on gas stoves or biomass fires without adequate ventilation are exposed to fine particle concentrations that exceed WHO safe limits. Air pollution exposure during pregnancy is associated with fetal growth restriction, preterm birth, impaired fetal lung development, and increased childhood asthma risk. Practical protective measures include improving kitchen ventilation, using an exhaust fan consistently while cooking, keeping windows open during cooking in cooler months, using a HEPA air purifier in the bedroom, and avoiding outdoor exposure during peak smog episodes in Rawalpindi and Islamabad.
Respiratory infections during pregnancy carry greater risks than in non-pregnant adults — both directly through their effects on maternal lung function and indirectly through inflammatory mediators that can trigger preterm labour. Do not manage respiratory infections with home remedies and wait-and-see approaches during pregnancy. Any respiratory infection with fever, breathlessness, or productive cough should be promptly evaluated by a physician. Antibiotics safe in pregnancy — amoxicillin, azithromycin — should not be withheld when bacterial infection is confirmed simply because of pregnancy. Untreated bacterial pneumonia in a pregnant woman is a serious condition.
Regular moderate physical activity during pregnancy — walking, swimming, prenatal yoga — improves cardiovascular fitness, maintains respiratory muscle strength, reduces the risk of excessive weight gain that worsens breathlessness and sleep apnea, and improves sleep quality. The recommendation of bed rest or avoiding all exertion during pregnancy is outdated advice for otherwise uncomplicated pregnancies. Discuss the appropriate level of activity for your specific pregnancy with your obstetrician and pulmonologist together, particularly if you have asthma or another respiratory condition.
When to Seek Urgent Medical Attention During Pregnancy
The following symptoms during pregnancy require prompt medical evaluation — do not wait for a scheduled antenatal visit if you experience any of these.
Respiratory Symptoms Requiring Urgent Assessment in Pregnancy
- Sudden severe breathlessness at rest — particularly if associated with chest pain or palpitations. This is a potential pulmonary embolism or cardiac emergency and requires emergency evaluation.
- Breathlessness that is rapidly worsening over hours to days — rather than the gradual physiological breathlessness of normal pregnancy progression.
- Wheeze that is not responding to your reliever inhaler — a severe asthma attack in pregnancy is a medical emergency requiring immediate treatment to protect both mother and fetus from hypoxia.
- Coughing up blood at any stage of pregnancy — always requires evaluation to exclude PE, pneumonia, and other serious causes.
- Fever above 38°C with cough and breathlessness — potential pneumonia requiring prompt antibiotic treatment.
- One-sided leg swelling, warmth, or pain alongside breathlessness — the combination suggests deep vein thrombosis with pulmonary embolism and requires emergency assessment.
- Persistent cough with weight loss or night sweats — TB investigation must not be delayed simply because of pregnancy. Early treatment protects both mother and fetus.
- Oxygen saturation below 95 percent on a pulse oximeter — if you have a pulse oximeter at home and your reading is consistently below 95 percent at rest during pregnancy, seek medical evaluation promptly.
Frequently Asked Questions
I have asthma and just found out I am pregnant. Should I stop my inhalers?
Absolutely not — and this is the most important message of this entire article for pregnant women with asthma. Stopping your inhaled corticosteroid preventer increases the risk of asthma exacerbations, which pose real dangers to your baby through repeated hypoxic episodes. The inhaled medications used to control asthma — particularly budesonide and salbutamol — have extensive safety data in pregnancy and are not associated with increased risks of congenital abnormalities or adverse pregnancy outcomes at standard doses. Continue your inhalers, book an urgent appointment with your pulmonologist to review your medications in the context of your pregnancy, and carry your reliever inhaler with you at all times.
I am getting breathless just walking across the room. Is this normal in pregnancy?
Mild breathlessness on moderate exertion is common and physiologically normal during pregnancy — driven by progesterone-stimulated hyperventilation, increased metabolic demand, and mechanical compression by the uterus. However, breathlessness that limits you at rest or with very minimal activity, that is rapidly worsening, or that is accompanied by wheeze, chest pain, palpitations, or leg swelling is not normal and requires medical evaluation. If you are in doubt — and particularly in the context of pregnancy, where the stakes involve your baby as well as yourself — it is always better to seek assessment and be reassured than to normalise a symptom that warrants investigation.
Is it safe to have a chest X-ray or CT scan during pregnancy?
A single chest X-ray exposes the fetus to an extremely small amount of radiation — far below the threshold associated with any risk of harm. It should not be withheld when clinically indicated. CT scanning delivers a higher radiation dose but remains below harmful thresholds for a single scan, particularly with appropriate fetal shielding. When serious conditions such as pulmonary embolism or pneumonia are suspected, the risk of delaying diagnosis — to both mother and fetus — substantially outweighs the minimal radiation risk from necessary imaging. The decision to perform chest imaging in a pregnant woman should be based on clinical need, with appropriate fetal protection where possible, and should not be prevented by unfounded radiation concerns.
My asthma has been well controlled for years. Is it likely to get worse during pregnancy?
As discussed above, approximately one third of women find asthma worsens during pregnancy. Even women with well-controlled disease before conception may experience deterioration — most commonly in the second trimester and triggered by respiratory infections. The best preparation is to ensure your baseline control is as good as possible before conception, to have a clear written asthma action plan, to attend regular pulmonology review throughout pregnancy, and to be vigilant about avoiding your known triggers. The fact that your asthma has been well controlled previously is a positive prognostic factor — but it does not eliminate the need for monitoring during gestation.
Can smog and air pollution during pregnancy harm my baby's lungs?
Yes — and the evidence for this is substantial and concerning. Air pollution exposure during pregnancy — particularly fine particulate matter (PM2.5) — is associated with fetal growth restriction, preterm birth, impaired fetal lung development, and significantly increased rates of childhood asthma and respiratory infections in the offspring. The lung development that begins in the womb and continues through early childhood is permanently shaped by the in-utero environment. Reducing air pollution exposure during pregnancy through indoor air purification, minimising outdoor exposure during high-AQI days in Rawalpindi and Islamabad, improving kitchen ventilation, and avoiding tobacco smoke exposure are all genuinely protective actions for your baby's respiratory future — not just your own.
Protecting Your Breath Protects Your Baby.
If you are pregnant and have a respiratory condition — or if you are experiencing breathlessness, cough, or any respiratory symptom that concerns you — a pulmonology consultation provides specialist assessment and clear guidance tailored to pregnancy. Book an appointment with Dr. Nabila Zaheer at PulmoCare today. Your lungs and your baby deserve the best possible care.
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