Hematological and Physiological Changes in Pregnancy

Pregnancy induces profound adaptations in maternal haematology and physiology to support foetal development and prepare for parturition. Plasma volume expands by up to 50%, leading to relative haemodilution and a fall in haemoglobin concentration despite a rise in red cell mass. Enhanced erythropoiesis and increased iron requirements accommodate this demand, while iron stores are mobilised to prevent maternal and foetal anaemia. Leucocyte counts, particularly neutrophils, rise progressively, reflecting innate immune activation, whereas lymphocyte and eosinophil proportions decline in late gestation. Platelet counts often decrease modestly due to increased consumption and dilution, but coagulation factors increase to create a hypercoagulable state that minimises haemorrhagic risk at delivery. Renal blood flow and glomerular filtration rate (eGFR) increase substantially, lowering serum creatinine and urea concentrations. Lipid metabolism shifts towards hyperlipidaemia, with elevated triglycerides, cholesterol and apolipoproteins, providing substrates for steroid hormone synthesis and foetal growth. Acute‐phase reactants such as C‐reactive protein and pentraxin‐3 rise in the third trimester without infection, reflecting a controlled inflammatory milieu essential for labour. Together, these dynamic changes underpin maternal–foetal nutrient exchange, immunotolerance and gestational homeostasis, with implications for screening, diagnosis and management of pregnancy‐related disorders.

Research from Nature Portfolio

A longitudinal proteomic analysis of maternal saliva revealed gestation‐dependent shifts in expression of 65 proteins involved in immune modulation, metabolism and host defence. Using data‐independent acquisition mass spectrometry, researchers clustered proteins into distinct trajectories across the first to third trimesters. Verification by targeted quantitative assays confirmed consistent patterns for a subset of immune‐related proteins, suggesting that non‐invasive salivary biomarkers may track systemic physiological adaptations and predict term birth outcomes.

Hematological and Physiological Changes in Pregnancy publication trend

The graph below shows the total number of articles in hematological and physiological changes in pregnancy across all publications each year (not limited to Nature Index journals).

Technical terms

Haemodilution: The reduction in blood cell concentration due to disproportionate expansion of plasma volume during pregnancy.

Erythropoiesis: The process by which new red blood cells are produced in the bone marrow, stimulated during gestation to meet increased oxygen demands.

C-reactive protein (CRP): An acute-phase protein produced by the liver that rises in response to systemic inflammation or tissue injury.

Glomerular filtration rate (eGFR): An estimate of the kidney’s filtering capacity, increased in pregnancy to enhance waste clearance and fluid balance.

Proteome: The entire complement of proteins expressed in a biological sample, reflecting dynamic physiological and pathological states.

References

1. Plasma C-Reactive Protein and Pentraxin-3 Reference Intervals During Normal Pregnancy. Frontiers in Immunology (2021).
2. Consecutive reference intervals for biochemical indices related to serum lipid levels and renal function during normal pregnancy. BMC Pregnancy and Childbirth (2022).
3. Salivary proteome signatures in the early and middle stages of human pregnancy with term birth outcome. Scientific Reports (2020).