hematologic changes of pregnancy
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Hematologic changes of pregnancy
Berhanu MohammedApril 21, 2011
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Hematology
Definition• Components of blood
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Components of blood
• Plasma– Transport mechanism
• 90-92% water. • 6-7% proteins• 2-3%
– Fats– Carbohydrates (glucose)– Electrolytes– Gases (O2, CO2)– Chemical messengers
Plasma Components
Other3%
Protein7%
Water90%
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Functions
• responsible for the transport of blood gases from the lung to the tissues (oxygen) and from the tissues back to the lungs (carbon dioxide).
• White blood cells serve to defend against pathogens and foreign bodies(immunity). They perform these tasks most of the time outside theblood vessels, in the connective tissues. In this case the blood serves solely as a means of transportation from the site of cell formation (bonemarrow) to the site of action.
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Cellular Components
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Components of blood
• Red Blood Cells– Erythrocyte
• Hemoglobin – O2 bearing molecule
– Comprised of 4 subunits:
» Globin (binds to 1 O2 molecule)
» Heme (iron)– 100% saturation = 4
globin subunits carrying O2
» Each gram of hemoglobin = 1.34 ml O2
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Fig. Formation of the multiple different blood cells from the original pluripotent hematopoietic stem cell (PHSC) in the bone marrow.04/13/2023
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Fig. Genesis of normal red blood cells (RBCs) and characteristics of RBCs in different types of anemias.04/13/2023
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Fig. Function of the erythropoietin mechanism to increase production of red blood cells when tissue oxygenation decreases.04/13/2023
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Genesis of white blood cells04/13/2023
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• Platelets (Thrombocytes)– Megakaryocytes
• Thrombopoietin
– Thrombocytopenia– Thrombocytosis
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Hemostasis
hemostasis is achieved by several mechanisms:1) vascular constriction, 2) formation of a platelet plug, 3) formation of a blood clot as a result of blood
coagulation, and4) eventual growth of fibrous tissue into the
blood clot to close the hole in the vessel permanently.
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Fig. Clotting process in a traumatized blood vessel.
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Schema for conversion of prothrombin to thrombin and polymerizationof fibrinogen to form fibrin fibers
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Extrinsic pathway for initiating blood clotting
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Ca++Intrinsic pathway for initiating blood clotting04/13/2023
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Pregnancy changes
The Most significant changes are:• Physiologic anemia• Neutrophilia • Mild thrombocytopenia • Increased procoagulant factors • Diminished fibrinolysis
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Plasma volume
• Increased by 10 to 15 % • Total gain at term averages 1100 to 1600mlTotal volume 4700ml to 5200ml ,i.e. 30 to 50% above non pregnant , Fig.1
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Fig.1
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Plasma Volume
Systemic vasodilatation
Rise in vascular capacitance
Underfilled vascular system
Rise in plasma volume
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Pregnancy-induced hypervolemia has important functions:
• To meet the metabolic demands of the enlarged uterus & hypertrophied vascular system.
• To provide an abundance of nutrients and elements to support the rapidly growing placenta and fetus.
• To protect the mother and in turn the fetus, against the deleterious effects of impaired venous return in the supine and erect positions.
• To safeguard the mother against the adverse effects of blood loss associated with parturition.
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Plasma Volume during postpartumDecreases
after delivery ,then increases
again 2 to 5 days later
10 to 15%
above
at 3 weeks
Nl at 6 wks
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RED BLOOD CELLS
• 20 to 30% (250 to 450 mL) above nonpregnant iron supplemented
• 15 to 20% above nonpregnant not on iron supplement
• Life span slightly decreased • Erythropoietin levels increase by 50 %
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Fig. Erythropoietin levels in response to anemia
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physiological or dilutional anemia of pregnancy
• Observed in healthy pregnant woman• Greatest during late 2nd to early 3rd trimester
lowest Hgb at 28 to 36wks • Nearer to term Hgb increases• Anemia cut off point: <11 g/dL 1st and 3rd
trimesters and < 10.5 g/dL 2nd trimester, for black Americans 0.8g/dl less
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Hemoglobin Values in Pregnancy
WEEKS' GESTATION
MEAN HEMOGLOBIN (G/DL)
FIFTH PERCENTILE HEMOGLOBIN (G/DL)
12 12.2 11.0
16 11.8 10.6
20 11.6 10.5
24 11.6 10.5
28 11.8 10.7
32 12.1 11.0
36 12.5 11.4
40 12.9 11.9
From U.S. Department of Health and Human Services: Recommendations to prevent and control iron deficiency in the United States. MMWR 47:1, 1998
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PLATELET COUNT
• Mean PLT slightly lower than healthy non pregnant woman
due to the effects of hemodilutionincreased platelet consumption
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Thrombocytopenia
• most significant obstetrical consideration concerning platelet physiology in pregnancy
• Gestational or incidental thrombocytopenia is characterized : mild asymptomatic occurring in the third trimester without any historynot associated with maternal, fetal, or neonatal
sequelae and spontaneously resolves postpartum Platelet counts are typically >70,000/microL, with
about two-thirds being 130,000 to 150,000 microL
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WHITE BLOOD CELLS
• 1st trimester, the mean count is 8,000/mm3, Nl (5,110 to 9,900/mm)
• 2nd & 3rd trimester, the mean is 8,500/mm3, Nl (5,600 to 12,200/mm3
• In labor, rise to 20,000 to 30,000/mm3, • largely due to increases in circulating segmented
neutrophils and granulocytes• caused by the elevated estrogen and cortisol levels • Returns to normal with in 1 to 2 weeks
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Immunologic system • associated with suppression humoral and cell-
mediated immunological functions • involve suppression of T-helper (Th) 1 and T-
cytotoxic (Tc) 1 cells, which decreases secretion of interleukin-2 (IL-2), interferon- , and tumor necrosis factor- (TNF-)
• upregulation of Th2 cells to increase secretion of IL-4, IL-6, and IL-13.
• In cervical mucus,immunoglobulins A and G (IgA and IgG) are significantly higher
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COAGULATION FACTORS AND INHIBITORS
• 5 to 6 fold increased risk for thromboembolic disease• venous stasis, vessel wall injury, and changes in the
coagulation cascade• Fibrinogen, factors II, VII, VIII, X, XII, and XIII increase
by 20 to 200 percent • Von Willebrand factor increases• Antithrombin, protein C, Factor V and Factor IX levels
remain unchanged or increase slightly• return to baseline by six to eight weeks after delivery
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Table 5-2. Changes in Measures of Hemostasis during Normal Pregnancy
Parameter Nonpregnant Pregnant (35–40 weeks)
Activated PTT (sec) 31.6 ± 4.9 31.9 ± 2.9
Thrombin time (sec) 18.9 ± 2.0 22.4 ± 4.1a
Fibrinogen (mg/dL) 256 ± 58 473 ± 72a
Factor VII (%) 99.3 ± 19.4 181.4 ± 48.0a
Factor X (%) 97.7 ± 15.4 144.5 ± 20.1a
Plasminogen (%) 105.5 ± 14.1 136.2 ± 19.5a
tPA (ng/mL) 5.7 ± 3.6 5.0 ± 1.5
Antithrombin III (%) 98.9 ± 13.2 97.5 ± 33.3
Protein C (%) 77.2 ± 12.0 62.9 ± 20.5a
Total Protein S (%) 75.6 ± 14.0 49.9 ± 10.2a
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Figure 3-11 The normal components of the coagulation cascade. (From Johnson RL: Thromboembolic disease complicating pregnancy. In Foley MR, Strong TH [eds]: Obstetric Intensive Care: A Practical Manual. Philadelphia, WB Saunders Company, 1997, p 91, with permission.)
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Key points Maternal plasma volume increases 50 percent
during pregnancy RBC volume increases approximately 18 to 30
percenthematocrit normally decreases during gestation but
not below 30 percent Pregnancy is a hypercoagulable state increases in the levels of the majority of the procoagulant factors increase and fibrinolytic system decreases and in some of the
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References
• Guyton and Hall ,Text book of medical physiology , 11th edition
• Williams Obstetrics,Cunningham, Leveno, Bloom, Hauth, Rouse, Spong, 23rd edition
• Obstetrics normal and problem pregnancies, Steven G. Gabbe,Jennifer R.Niebyl, Joe leigh simpson, 5th Edition
• Up to date , 18.2
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Thank you
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