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Shortness of breath in pregnancy: what's normal, and when to call

Feeling short of breath is one of the most common symptoms of pregnancy, and usually a sign the body is doing exactly what it should. Usually - which is why the warning signs matter.

3 min read · Updated 2026-11-08

Why it happens, even early on

Breathlessness in pregnancy often starts in the first trimester, long before the bump is big enough to press on anything. The cause is hormonal. Progesterone makes the brain's breathing centre more sensitive to carbon dioxide, so you breathe more air per minute - mostly by taking deeper breaths rather than faster ones [1].

The result is a lower level of carbon dioxide in the blood, which helps carbon dioxide pass from the baby to you across the placenta. It is a useful adaptation, and many people experience it as a feeling of not quite getting enough air, even though their oxygen levels are fine. This is common enough to have its own name: physiological breathlessness of pregnancy.

Later on: less room for the diaphragm

From the second trimester, the growing uterus pushes the diaphragm upwards. The body compensates by widening the lower ribcage, which flares outward and keeps lung capacity roughly where it was [1]. Breathing that used to go into the belly now has to go sideways and back instead.

This is the reason for rib room breathing: hands on the sides of the lower ribs, breathe so that the ribs widen into your palms while the shoulders stay still. It does not change the hormones or make the baby smaller, but many people find that directing the breath sideways makes each breath feel fuller and stops the shallow upper-chest breathing that makes breathlessness feel worse.

Many people feel some relief in the final weeks, when the baby moves down into the pelvis and takes some of the pressure off the diaphragm.

What helps day to day

Posture makes a real difference. Slumping squeezes the ribcage from above as well as below; sitting and standing tall gives it room. Taking stairs and hills more slowly, and pausing to let the breath settle, is not a weakness - your heart and lungs are working harder than they were before pregnancy.

Slow breathing with a longer exhale than inhale helps with the anxious edge that breathlessness can bring, which tends to make it worse. It is worth practising when you feel fine, so it is familiar when you do not.

At night, many people find lying propped up or on their side easier. Later in pregnancy, going to sleep on your side rather than your back is recommended anyway: an analysis of several studies found that going to sleep on the back in the third trimester was associated with a higher risk of late stillbirth [2]. Waking up on your back is common and not a reason to worry; just turn back onto your side.

What breathing practice cannot do

Breathing exercises can make normal pregnancy breathlessness more comfortable. They cannot treat breathlessness that has another cause, and they should never be used to talk yourself out of a symptom that is new, sudden or getting worse.

Avoid breath holds and forceful, fast breathing during pregnancy. The pregnancy section of this app leaves those out entirely rather than flagging them with a warning.

When it is not normal

Pregnancy raises the risk of blood clots, including a clot in the lungs (pulmonary embolism), which is rare but serious [3]. It can also unmask or worsen asthma, anaemia and, rarely, heart problems.

Get medical help straight away - call your maternity unit, your doctor, or emergency services - if breathlessness comes on suddenly; if it comes with chest pain, coughing up blood, or a racing or irregular heartbeat; if you feel faint; if you are breathless at rest or lying flat when you were not before; or if you also have swelling, pain or redness in one leg.

Also tell your midwife or doctor if breathlessness comes with a severe headache, vision changes or sudden swelling of the face and hands, which can be signs of pre-eclampsia, or if it is steadily getting worse. If you are not sure, ask: nobody in maternity care minds being called about breathlessness. This page is general information, not medical advice.

References

  1. LoMauro A, Aliverti A. Respiratory physiology of pregnancy. Breathe, 2015. Link
  2. Cronin RS, Li M, Thompson JMD, et al. An individual participant data meta-analysis of maternal going-to-sleep position, interactions with fetal vulnerability, and the risk of late stillbirth. EClinicalMedicine, 2019. Link
  3. Royal College of Obstetricians and Gynaecologists. Reducing the risk of venous thromboembolism during pregnancy and the puerperium (Green-top Guideline No. 37a), 2015.

Techniques mentioned

General information about breathing practices, not medical advice. How this is written and sourced.