Cardiovascular and haematological changes of normal pregnancy
How blood volume, cardiac output, heart rate and systemic vascular resistance change through pregnancy, labour and the puerperium, with worked cardiac output and SVR calculations; normal examination, ECG and echo findings; why stenotic valves decompensate and regurgitant ones don't; dilutional anaemia and Australian haemoglobin thresholds; white cells, gestational thrombocytopenia, and the procoagulant shift that raises VTE risk and D-dimer.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Plasma volume rises 40 to 50% but red cell mass only 20 to 30%, so haemoglobin falls: physiological dilutional anaemia.
- Cardiac output rises 30 to 50%, mostly by 20 to 24 weeks. SVR falls 30 to 40% and blood pressure dips in the second trimester.
- The highest-risk moments for heart disease are the late second trimester (peak volume load), labour, and the first hours after delivery.
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Sources
- 2025 ESC Guidelines for the management of cardiovascular disease and pregnancy. De Backer J, Haugaa KH et al. Eur Heart J 2025;46(43):4462-4568European Society of Cardiology, 2025
- Patient Blood Management Guidelines: Module 5 Obstetrics and MaternityAU/NZNational Blood Authority Australia, 2015
- Guideline on haemoglobin cutoffs to define anaemia in individuals and populationsWorld Health Organization, 2024
- The SOMANZ position statement on pulmonary embolism in pregnancy and post-partumAU/NZSociety of Obstetric Medicine of Australia and New Zealand (Lowe SA, Barrett HL, Cutts BA et al.), 2021
- Physiological changes in pregnancy. Soma-Pillay P, Nelson-Piercy C, Tolppanen H, Mebazaa A. Cardiovasc J Afr 2016;27:89-94Cardiovascular Journal of Africa, 2016
- Last updated
- 14 November 2026
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