Hematologic changes of pregnancy

1. Hematologic changes of pregnancy Berhanu Mohammed April 21, 2011  

2. Hematology Definition Components of blood 4/24/2011

3. Components of blood Plasma Transport mechanism 90-92% water. 6-7% proteins 2-3% Fats Carbohydrates (glucose) Electrolytes Gases (O 2 , CO 2 ) Chemical messengers 4/24/2011

4. 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 the blood 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. 4/24/2011

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6. Cellular Components 4/24/2011

7. Components of blood Red Blood Cells Erythrocyte Hemoglobin – O 2 bearing molecule Comprised of 4 subunits: Globin (binds to 1 O 2 molecule) Heme (iron) 100% saturation = 4 globin subunits carrying O 2 Each gram of hemoglobin = 1.34 ml O 2 4/24/2011

8. Fig. Formation of the multiple different blood cells from the original pluripotent hematopoietic stem cell (PHSC) in the bone marrow. 4/24/2011

9. Fig. Genesis of normal red blood cells (RBCs) and characteristics of RBCs in different types of anemias. 4/24/2011

10. Fig. Function of the erythropoietin mechanism to increase production of red blood cells when tissue oxygenation decreases. 4/24/2011

11. Genesis of white blood cells 4/24/2011

12. Platelets (Thrombocytes) Megakaryocytes Thrombopoietin Thrombocytopenia Thrombocytosis 4/24/2011

13. 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, and 4) eventual growth of fibrous tissue into the blood clot to close the hole in the vessel permanently. 4/24/2011

14. Fig. Clotting process in a traumatized blood vessel. 4/24/2011

15. Schema for conversion of prothrombin to thrombin and polymerizationof fibrinogen to form fibrin fibers 4/24/2011

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17. Extrinsic pathway for initiating blood clotting 4/24/2011

18. Ca++ Intrinsic pathway for initiating blood clotting 4/24/2011

19. Pregnancy changes The Most significant changes are: Physiologic anemia Neutrophilia Mild thrombocytopenia Increased procoagulant factors Diminished fibrinolysis 4/24/2011

20. Plasma volume Increased by 10 to 15 % Total gain at term averages 1100 to 1600ml Total volume 4700ml to 5200ml , i.e. 30 to 50% above non pregnant , Fig.1 4/24/2011

21. Fig.1 4/24/2011

22. Plasma Volume Systemic vasodilatation Rise in vascular capacitance Underfilled vascular system Rise in plasma volume 4/24/2011

23. 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. 4/24/2011

24. Plasma Volume during postpartum 4/24/2011

25. 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 % 4/24/2011

26. 4/24/2011 Fig. Erythropoietin levels in response to anemia

27. physiological or dilutional anemia of pregnancy Observed in healthy pregnant woman Greatest during late 2 nd to early 3 rd trimester lowest Hgb at 28 to 36wks Nearer to term Hgb increases Anemia cut off point: <11 g/dL 1 st and 3 rd trimesters and < 10.5 g/dL 2 nd trimester, for black Americans 0.8g/dl less 4/24/2011

28. 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 4/24/2011

29. PLATELET COUNT Mean PLT slightly lower than healthy non pregnant woman due to the effects of hemodilution increased platelet consumption 4/24/2011

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31. 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 history not 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 4/24/2011

32. WHITE BLOOD CELLS 1 st trimester, the mean count is 8,000/mm 3 , Nl (5,110 to 9,900/mm) 2 nd & 3 rd trimester, the mean is 8,500/mm 3 , Nl (5,600 to 12,200/mm 3 In labor, rise to 20,000 to 30,000/mm 3 , 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 4/24/2011

33. 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 4/24/2011

34. 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 4/24/2011

35. 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 ± 4.1 a Fibrinogen (mg/dL) 256 ± 58 473 ± 72 a Factor VII (%) 99.3 ± 19.4 181.4 ± 48.0 a Factor X (%) 97.7 ± 15.4 144.5 ± 20.1 a Plasminogen (%) 105.5 ± 14.1 136.2 ± 19.5 a 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 ± 20.5 a Total Protein S (%) 75.6 ± 14.0 49.9 ± 10.2 a 4/24/2011

36. 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.) 4/24/2011

37. Key points Maternal plasma volume increases 50 percent during pregnancy RBC volume increases approximately 18 to 30 percent hematocrit 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 natural inhibitors of coagulation 4/24/2011

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40. References Guyton and Hall ,Text book of medical physiology , 11 th edition Williams Obstetrics,Cunningham, Leveno, Bloom, Hauth, Rouse, Spong, 23 rd edition Obstetrics normal and problem pregnancies, Steven G. Gabbe,Jennifer R.Niebyl, Joe leigh simpson, 5 th Edition Up to date , 18.2 4/24/2011

41. Thank you 4/24/2011

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