Breathlessness in pregnancy: a case-based approach

The case: mild breathlessness at 28 weeks

A woman who is 28 weeks pregnant notices she gets short of breath walking upstairs, something she managed easily before. She feels well otherwise, with no chest pain, no cough and no leg swelling on one side more than the other. Her breathing settles quickly with rest. This kind of gradual, effort-related breathlessness is extremely common in pregnancy. The growing womb pushes up on the diaphragm, and hormonal changes make you breathe a little deeper. Many healthy pregnant women feel more puffed than usual. The clinician's job is to separate this normal shift from the smaller number of cases where breathlessness points to a problem needing urgent action.

Why pregnancy raises clot risk

Pregnancy makes the blood more likely to clot. This is the body's way of guarding against heavy bleeding at birth, but it also raises the risk of a clot forming in a leg vein (a deep vein thrombosis) that can break off and travel to the lung. That lung clot is a pulmonary embolism, and it remains a leading cause of serious illness in pregnancy and the weeks afterwards. The risk is higher if you have had a clot before, have a family history, are less mobile, are carrying extra weight, or have just had a caesarean. Because of this raised background risk, clinicians keep pulmonary embolism firmly in mind whenever a pregnant woman reports new or sudden breathlessness.

The warning signs that change the plan

Certain features shift breathlessness from likely-normal to urgent. Sudden breathlessness that comes on quickly, chest pain that is sharp or worse when breathing in, coughing up blood, a racing heartbeat, or feeling faint all raise concern for a clot on the lung. A painful, swollen, red or warm calf — usually on one side — suggests a clot in the leg that could travel. In our illustrative case, if the woman suddenly became much more breathless, developed chest pain or noticed a swollen calf, that would prompt emergency assessment. These are the signals that a clinician cannot safely wait on, and they are the reason breathlessness is never simply brushed aside in pregnancy.

How doctors assess and investigate

Assessment starts with careful questions and an examination: how fast breathlessness came on, any chest pain or leg swelling, oxygen levels, heart rate and blood pressure. If a clot on the lung is suspected, imaging is arranged, usually a scan of the lung's blood vessels or its air spaces, chosen to keep radiation to mother and baby as low as possible. An ultrasound of the legs may look for a clot there. Standard clot-risk scores used in non-pregnant adults are not relied upon in pregnancy, and the blood test called a D-dimer is less useful because it naturally rises in pregnancy. Doctors therefore lean on the story, the examination and appropriate imaging rather than a single number.

Reassurance, treatment and follow-up

Most pregnant women with breathlessness are reassured after assessment: their symptom reflects the normal demands of pregnancy or a minor cause such as a cold or low iron levels, which can be checked with a blood test. When a clot is confirmed, treatment with blood-thinning injections is started promptly and continued through pregnancy and for a period afterwards, under specialist care. The key message from this case is balance: breathlessness in pregnancy is usually harmless, but sudden breathlessness, chest pain, coughing up blood or a swollen calf need urgent medical attention. Knowing which is which is exactly the judgement clinicians are trained to make, and why they would rather assess and reassure than miss a rare but serious clot.