Chuyên đề huyết học (tiếng anh)
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Chuyên đề huyết học (tiếng anh)
Maternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) to accommodate the growing and developing fetoplacental unit. The major hematologic changes during pregnancy include expanded plasma volume, physiologic anemia, mild neutrophilia in some individuals, and a mildly prothrombotic state. The clinician must be able to distinguish these anticipated physi Chuyên đề huyết học (tiếng anh) ologic changes from those caused by pregnancy-related complications.This topic discusses physiologic changes in blood volume, blood cells, and hemostaChuyên đề huyết học (tiếng anh)
sis during pregnancy. Cardiovascular and vascular changes associated with pregnancy and hematologic complications of pregnancy are discussed in separaMaternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) he adult with unexplained neutropenia".)•(See "Thrombocytopenia in pregnancy".)OVERVIEWThe most significant hematologic changes during pregnancy include the following and are detailed in the table (table 1):•Expanded plasma volume (in excess of the increase in red blood cell mass) and resultant phys Chuyên đề huyết học (tiếng anh) iologic anemia•Mild neutrophilia•Mild thrombocytopenia•Increased procoagulant factors and decreased natural anticoagulants•Diminished fibrinolysisFINDChuyên đề huyết học (tiếng anh)
INGS OF CONCERNThe following findings are not consistent with normal, physiologic adaptation to pregnancy and should prompt additional evaluation, andMaternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) a or polycythemia, especially when associated with symptoms out of proportion to the stage of pregnancy. Hemoglobin levels less than 10 g/dL or greater than 16 g/dL should prompt hematologic evaluation unless the etiology is known or the abnormalities are related to a preexistent chronic condition. Chuyên đề huyết học (tiếng anh) (See "Anemia in pregnancy" and "Clinical manifestations and diasnpsis .QÍ ,p.Q]y.cy.thgmia y.eia"..)1•Evidence of iron deficiency (eg, new microcytosiChuyên đề huyết học (tiếng anh)
s, which is a late finding of iron deficiency, or iron studies showing reduced iron stores). The demand for iron is increased in pregnancy (figure 1):Maternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) e, pregnant women can have iron deficiency anemia with ferritin levels in the low-normal reference range.While oral iron supplementation in prenatal vitamins is standard, this may not be sufficient tor women with iron deficiency, and oral iron supplements are often poorly tolerated because of gastri Chuyên đề huyết học (tiếng anh) c irritation and/or constipation. Thus, parenteral iron administration should be considered in women with iron deficiency anemia who do not respond toChuyên đề huyết học (tiếng anh)
or cannot tolerate oral iron supplementation. (See "Anemia in pregnancy", section on 'Management'.)•Thalassemia is another major cause of microcytic Maternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) ia. Leukocytosis due to an excess of neutrophils can occur in some women during pregnancy in the absence of infection or inflammatory conditions. Findings prompting hematology consultation include a white blood cell (WBC) count >20,000/microL in the absence of labor or infection, or a WBC differenti Chuyên đề huyết học (tiếng anh) al showing immature myeloid or lymphoid forms or a marked excess of lymphocytes. Leukopenia in association with an absolute neutrophil count <1000/micChuyên đề huyết học (tiếng anh)
roL that is unexplained also requires hematologic evaluation. (See L'App£QàdJLtQ_die-p.a.tiein with neutrophilia" and 2AppmadU0_ the adult with unexplMaternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) between 80,000 and 149,000/microL) is common dining pregnancy. Levels below this level should prompt hematologic consultation. (See "Thrombocytopenia in pregnancy".)•Thrombocytosis, rhe new onset of thrombocytosis is unusual during pregnancy, and platelet counts >500,000/microL should prompt hemato Chuyên đề huyết học (tiếng anh) logic evaluation. Platelet counts >l,000,000/microL require urgent evaluation.(See "Approach to the patient with thrombocx tosis" and "Diagnosis and cChuyên đề huyết học (tiếng anh)
linical manifestations of essential thrombocx lhemia".)PLASMA VOLUMEPlasma volume increases by 10 to 15 percent at 6 to 12 weeks of gestation, expandsMaternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) ml. and results in a total plasma volume of 4700 to 5200 ml., which is 30 to 50 percent above that in nonpregnant women 11,4,51. The expanded plasma volume is thought to meet the increased metabolic demands of2(he uterus and placenta, facilitate delivery of nutrients to the developing fetus and remo Chuyên đề huyết học (tiếng anh) val of waste, protect against the effects of impaired venous return when the mother is supine or standing, and protect the mother from excessive bloodChuyên đề huyết học (tiếng anh)
loss during delivery [6].During pregnancy, plasma renin activity tends to be increased and atrial natriuretic peptide levels are slightly reduced [7.Maternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) se in vascular capacitance. The converse picture (low plasma renin activity and elevated natriuretic peptide, suggestive of a vascular response to expanded plasma volume) are not seen. The hypothesis that vascular changes precede expansion of the plasma volume is also supported by the observation th Chuyên đề huyết học (tiếng anh) at increasing sodium intake does not lead to further volume expansion [9]. Of note, total plasma volume expansion is accompanied by retention of 900 tChuyên đề huyết học (tiếng anh)
o 1000 mEq of sodium and 6 to 8 L of water, which is distributed among the fetus, amniotic fluid, and extracellular and intracellular spaces (9.101.ThMaternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) ld reverse or prevent associated poor pregnancy outcomes associated with low plasma volume. In theory, increasing dietary protein could improve colloid oncotic pressure (COP), which would shift extravascular fluid to the intravascular space. For dehydrated women, increasing maternal hydration may al Chuyên đề huyết học (tiếng anh) so act synergistically with a higher COP to improve intravascular volume.RED BLOOD CELLSIncreased mass — Red blood cell (RBC) mass begins to increaseChuyên đề huyết học (tiếng anh)
at 8 to 10 weeks of gestation, steadily rises, and reaches levels 20 to 30 percent higher than in nonpregnant women by the end of pregnancy [4,11-141.Maternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) increase in RBC mass is smaller than the increase in plasma volume, which contributes to the physiologic anemia of pregnancy. (See 'Dilutional or physiologic anemia' below.)The increase in RBC mass requires sufficient iron, folate, and vitamin B12; thus, women with deficiencies of iron or these vit Chuyên đề huyết học (tiếng anh) amins will have blunted increases in RBC mass and are likely to develop more severe anemia. As an example, in a series of 69 women not receiving ironChuyên đề huyết học (tiếng anh)
supplements, the RBC mass was estimated to increase by 15 to 20 percent rather than the normal 20 to 30 percent and the MCV decreased to an average vaMaternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) uction [61. Erythropoietin levels increase by 50 percent in normal pregnancies and vary according to the presence of pregnancy complications 1181. RBC lifespan is also slightly decreased during normal pregnancy L19J.I he increased RBC mass partially supports the higher metabolic requirement for oxyg Chuyên đề huyết học (tiếng anh) en during pregnancy [201. In addition, levels of RBG 2,3 bisphosphoglycerate (2,3-BPG, also called 2,3-diphosphoglycerate [2,3-DPGJ) remain elevated dChuyên đề huyết học (tiếng anh)
uring pregnancy, which leads to a decrease in oxygen affinity (ie, a shift of the hemoglobin-oxygen dissociation curve to the right) (figure 3) [21Ị. Maternal adaptations to pregnancy: Hematologic changesINTRODUCTIONNormal pregnancy is characterized by profound changes in almost ever}' organ system Chuyên đề huyết học (tiếng anh) he placenta and to the fetal RBGs, which have greater oxygen affinity due to fetal hemoglobin. The function of fetal hemoglobin is reviewed elsewhere.Gọi ngay
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