Physiological Dynamics of Blood Volume in Pregnancy
Summary
During pregnancy, maternal blood volume undergoes a marked and well-orchestrated expansion to accommodate the increased metabolic and circulatory demands of both mother and foetus. This hypervolaemic adaptation begins in the first trimester with a modest rise in plasma volume, accelerates during the second trimester, and peaks in the late third trimester with total blood volume increases of up to 40–50% above pre-pregnancy levels. Key drivers include rising oestrogen and progesterone levels, activation of the renin–angiotensin–aldosterone system and a reduction in systemic vascular resistance, all contributing to fluid retention and vascular compliance. The augmented plasma volume supports enhanced uteroplacental perfusion, buffers against intrapartum haemorrhage and maintains maternal cardiovascular stability. Aberrations in this expansion pattern have been linked to conditions such as preeclampsia, foetal growth restriction and peripartum cardiomyopathy. Recent advances in non-invasive monitoring and molecular characterisation of vascular adaptation are shedding light on the interplay between maternal characteristics—such as body mass index and pre-existing hypertensive disorders—and the regulation of blood volume dynamics across diverse populations.
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Physiological Dynamics of Blood Volume in Pregnancy publication trend
The graph below shows the total number of articles in physiological dynamics of blood volume in pregnancy across all publications each year (not limited to Nature Index journals).
Technical terms
Plasma volume expansion: Increase in the liquid component of blood during pregnancy to support enhanced maternal and foetal circulation.
Haemodilution: Reduction in the concentration of blood cells and solutes caused by the disproportionate rise in plasma volume.
Intravascular compartment: The portion of the circulatory system within blood vessels containing plasma and formed blood elements.
Indocyanine green (ICG) dye: A fluorescent tracer dye used to quantify plasma volume by analysing its dilution and clearance kinetics.
References
- Plasma volume expansion across healthy pregnancy: a systematic review and meta-analysis of longitudinal studies. BMC Pregnancy and Childbirth (2019).
- An efficient method for measuring plasma volume using indocyanine green dye. MethodsX (2019).
- Modern approaches to the infusion therapy of preeclampsia and eclampsia. EMERGENCY MEDICINE (2022).
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