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Vera Ignjatović: The Changing Balance of Hemostasis Across Childhood
Vera Ignjatović/researchgate.net
Nov 11, 2026, 13:52

Vera Ignjatović: The Changing Balance of Hemostasis Across Childhood

Vera Ignjatović, Founder and Managing Director at Ignis Innovations Pty Ltd, Principal Consultant of Translational Research at Johns Hopkins All Children’s Hospital, shared a post on LinkedIn about a recent article she and her colleagues co-authored, published in JTH, adding:

“Birth is perfection, and it is all downhill from there.

The hemostatic system of infants and children is not a work in progress.

It is a physiological masterclass!

By adult standards, a newborn’s blood looks deficient.

This is because the concentration of several key clotting proteins (the vitamin K-dependent coagulation factors) is approximately 30 percent to 50 percent of adult values.

However, healthy term newborns generate thrombin (key clotting protein) comparably to adults.

As a result, healthy babies and children do not, as a rule, spontaneously bleed or form blood clots, and their baseline risk of thrombosis is significantly lower compared to adults.

The reason is age-specific recalibration.

Every apparent ‘shortfall’ is matched by reciprocal changes elsewhere in the system, so the overall hemostatic potential is maintained:

  • Lower concentration of clotting proteins, but more of a potent ‘glue’ that helps platelets seal a wound (von Willebrand factor, at  approximately 150 percent of adult levels and rich in its most functionally active ultra-large multimers).
  • Lower concentration of physiological anticoagulants (protein C, protein S and antithrombin), but high levels of a protective protein that keeps clotting in check (alpha-2-macroglobulin, with significant thrombin-inhibitory capacity).

This is developmental hemostasis, a blood clotting system that is not underdeveloped but precisely designed and calibrated for its physiological context.

Yet the word ‘immature’ persists in textbooks, clinical guidelines and publications.

In our new Forum article in the Journal of Thrombosis and Haemostasis (JTH), we argue that this label is not only scientifically imprecise but clinically consequential.

The immature label encourages:

  • interpreting children’s results against adult values rather than age- and assay-specific reference ranges
  • ‘correcting’ individual proteins towards adult levels, risking overtreatment
  • extrapolating adult data to pediatric dosing, guidelines and trials

We call on the hemostasis community to retire the language of immaturity in favor of ‘developmentally regulated’, ‘physiologically adapted’ and, preferably, ‘age-appropriate’.

And we leave the question… does the adult hemostatic system represent a deterioration from childhood peak functionality?

Thank you to my co-authors Chantal Attard, Steven Bruzek, Marisol Betensky, Maha Al-Ghafry, Neil Goldenberg and Paul Monagle.”

Title: Not immature, but perfect for age: the hemostatic system of infants and children as a physiological masterclass

Authors: Vera Ignjatovic, Chantal Attard, Steven Bruzek, Marisol Betensky, Maha Al-Ghafry, Neil Goldenberg, Paul Monagle

Vera Ignjatović: The Changing Balance of Hemostasis Across Childhood

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Chantal Attard Health Hematology Hemostasis Hemostasis News Hemostasis Today Journal of Thrombosis and Haemostasis JTH Maha Al-Ghafry Marisol Betensky Medicine Neil Goldenberg Paul Monagle protein C protein S Steven Bruzek Vera Ignjatovic Von Willebrand Factor
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