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Evolution of blood coagulation activators and inhibitors in the healthy human fetus
P Reverdiau-Moalic1, B Delahousse, G Body
1Laboratoire d'Hématologie-Hémostas Foetale, Groupe Interactions Hôte-Greffon, Faculté de Médecine, Tours, France.
Insights
Fetal blood coagulation factors are low during pregnancy, impacting clotting times. Factor levels increase later in gestation, gradually reaching adult levels after birth, indicating a dynamic developmental process.
Area of Science:
- Hematology
- Developmental Biology
- Pediatric Medicine
Background:
- Fetal hemostasis differs significantly from adult hemostasis.
- Understanding fetal coagulation is crucial for managing neonatal bleeding disorders.
Purpose of the Study:
- To characterize the developmental profile of blood coagulation proteins in healthy fetuses.
- To compare fetal coagulation factor levels with those of newborns and adults.
Main Methods:
- Coagulation screening tests (prothrombin time, activated partial prothrombin time, thrombin clotting time) were performed.
- Levels of specific coagulation factors (vitamin K-dependent, contact factors, V, VIII, fibrinogen) were measured.
- Immunologic and functional assays were used to identify potential fetal-specific proteins.
Main Results:
- Fetuses exhibited prolonged clotting times due to lower levels of most coagulation factors and inhibitors.
- Levels of most coagulation factors and inhibitors increased after 34 weeks of gestation.
- Only factors V and VIII reached adult levels by birth, highlighting gradual maturation.
Conclusions:
- Fetal hemostasis is a dynamic system that matures progressively throughout gestation.
- The gradual increase in coagulation factors supports a transition from a fetal to a neonatal and then adult hemostatic state.
Abstract:
Blood coagulation proteins were determined in 285 healthy fetuses from 19 to 38 weeks' gestation and compared with those of 60 normal full-term newborns and 40 adult controls. Prolongation of the coagulation screening tests, prothrombin time, activated partial prothrombin time, and thrombin clotting time, in fetuses throughout intrauterine life was explained by low levels of vitamin K-dependent factors (II, VII, IX, and X), contact factors (XI, XII, prekallikrein, and high-molecular-weight kininogen), factor V, factor VIII, and fibrinogen. Low levels of antithrombin III, heparin cofactor II, protein C and protein S, and tissue factor pathway inhibitor were also found, and these probably contributed to a satisfactory hemostatic balance. Some of these parameters were evaluated by both immunologic and functional assays to detect possible "fetal" proteins. An increase in factor levels was observed after the thirty-fourth week of intrauterine life for most of the coagulation activators and inhibitors, but only factors V and VIII reached adult values at birth. This study therefore showed that fetal hemostasis is a dynamic system that evolves gradually toward the neonatal state and then toward the adult state.