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ACOG Pub Review > PB#78: Hemoglobinopathies In Pregnancy > Flashcards

PB#78: Hemoglobinopathies In Pregnancy Flashcards

1
Q

Number of interlocking polypeptide chains per Hgb

A

Four

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2
Q

Possible Hgb polypeptide chains (6)

A

α, β, γ, δ, ε, ζ

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3
Q

Possible structures of adult Hgb (3)

A

Hgb A, Hgb F, Hgb A2

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4
Q

Structure of Hgb A

A

Two α-chains + two β-chains

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5
Q

Structure of Hgb F

A

Two α-chains + two γ-chains

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6
Q

Structure of Hgb A2

A

Two α-chains + two δ-chains

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7
Q

Gestational ages from which Hgb F is primary Hgb

A

12-24wga

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8
Q

Transition from Hgb F to Hgb A

A

3rd tri (via increased production of β-chains

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9
Q

Location of genes that code for α-chain

A

Short arm of chromosome 16

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10
Q

Location of genes that code for β-chain

A

Short arm of chromosome 11

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11
Q

Inheritance of SCD

A

Autosomal recessive

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12
Q

Nucleotide substitution that changes Hgb A to Hgb S

A

T>A in β-chain

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13
Q

Amino acid substitution that changes Hgb A to Hgb S

A

Val>gln at position 6 of β-chain

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14
Q

Nucleotide substitution that changes Hgb A to Hgb C

A

A>G in β-chain

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15
Q

Amino acid substitution that changes Hgb A to Hgb C

A

Lys>gln

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16
Q

Condition that arises in Hgb S heterozygote; condition that arises in Hgb S homozygote

A

SCT; sickle cell anemia

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17
Q

Condition that arises from Hgb S heterozygote + Hgb C heterozygote

A

Hgb SC disease (can also cause SCD)

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18
Q

Other hemoglobinopathy combos that can cause clinically significant SCD

A

Hgb S/β-thalassemia

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19
Q

Demographic w/ highest rate of SCD

A

Blacks

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20
Q

Rate of SCT, rate of SCD, rate of sickle cell anemia among black individuals

A

1 in 12, 1 in 300, 1 in 600

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21
Q

Other demographics (besides Blacks) w/ higher frequency of Hgb S (6)

A

Greeks, Italians (particularly Sicilians), Turks, Arabs, Southern Iranians, Indians

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22
Q

Physiologic features of RBCs in SCD

A

Distortion (sickling) of RBCs when under O2 tension, leading to increased viscosity/hemolysis/anemia w/ further decrease in oxygenation

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23
Q

Etiology of vaso-occlusive crises

A

Sickling in small vessels can lead to logjams that interrupt blood supply to vital organs

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24
Q

Potential outcome of repeated vaso-occlusive crises

A

Widespread microvascular obstruction w/ interruption of normal perfusion/function of several organs (spleen/lungs/kidneys/heart/brain)

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25
Q

Consideration for adults w/ SCD (re a specific organ)

A

Functional asplenia 2/2 autosplenectomy by adolescence; resultant increased incidence/severity of infections

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26
Q

Most significant threat to pts w/ SCD

A

Acute chest syndrome

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27
Q

Clinical characteristics of ACS

A

Pulmonary infiltrates (not infectious in origin, but rather 2/2 vaso-occlusion from sickling or embolization of marrow from long bones affected by sickling) w/ fever that leads to hypoxemia/acidosis

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28
Q

How to diagnose SCD

A

Hgb electro

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29
Q

Hgb electro results for SCD/Hgb SS

A

Nearly all Hgb S, w/ small amount of Hgb A2 and Hgb F

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30
Q

Hgb electro results in SCT/Hgb AS

A

Large percentage of Hgb S, though also w/ larger percentage of Hgb A than in SCD

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31
Q

General characteristics of thalassemias

A

Reduced synthesis of globin chains, resulting in microcytic anemia

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32
Q

Genetic cause of α-thal

A

Gene deletion of 2+ copies of the four α-chains

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33
Q

Allele notation, lab testing, and clinical course when one α-chain is deleted

A

(α-/αα), mild asymptomatic microcytic anemia, clinically unrecognizable

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34
Q

Condition, lab testing when two α-chains are deleted

A

α-thal trait/α-thal minor, mild asymptomatic microcytic anemia

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35
Q

Two possible allele notations for α-thal trait

A

αα/– (cis), α-/α- (trans)

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36
Q

Primary concern for α-thal carriers

A

Increased risk for having offspring w/ more severe α-thal

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37
Q

Demographics w/ higher rates of α-thal trait (4)

A

Southeast Asians, Blacks, West Indians, Mediterraneans

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38
Q

Allele formation more often seen in Southeast Asians w/ α-thal trait, and clinical concern for offspring

A

More likely to have cis deletion, so offspring at higher risk for Hgb Bart’s or Hgb H disease

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39
Q

Allele formation more often seen in Blacks w/ α-thal trait, and clinical concern for offspring

A

More likely to have trans deletion, so offspring typically do not develop Hgb Bart’s

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40
Q

Condition, allele notation, lab testing when three α-chains are deleted

A

Hgb H disease, α-/–, mild-mod hemolytic anemia

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41
Q

Condition, allele notation when four α-chains are deleted

A

α-thal major (Hgb Bart’s), –/–

42
Q

Fetal risks associated w/ α-thal major/Hgb Bart’s (3)

A

Hydrops fetalis, IUFD, pre-E

43
Q

Can you inherit α-thal and SCT/SCD?

A

Yes (because Hgb S affects β-chain and α-thal affects α-chain)

44
Q

Effect of α-thal on pts w/ SCT; effect of α-thal on pts w/ SCD

A

Lowers proportion of Hgb S; lessens severity of SCD

45
Q

Alternative genetic etiology for α-thal (instead of gene deletion)

A

Gene mutation (so genes are present but not functioning normally)

46
Q

Hgb Constant Spring

A

Mutation in stop codon, leading to synthesis of longer/unstable α-chain

47
Q

Hgb Qong Sze

A

Substitutions impairing αβ dimer formation

48
Q

αTSaudi

A

Point substitutions in poly A region at 3’ end of gene

49
Q

Genetic cause of β-thal

A

Mutation in β-chain gene, causing deficient or absent β-chain production, resulting in absence of Hgb A

50
Q

Clinical condition associated w/ heterozygous β-chain mutation

A

β-thal minor

51
Q

Clinical conditions associated w/ homozygous β-chain mutation (2)

A

β-thal major (Cooley’s anemia), β-thal intermedia (milder form)

52
Q

Clinical sxs associated w/ β-thal major

A

Severe anemia w/ resultant extramedullary erythropoiesis, delayed sexual development, poor growth

53
Q

Considerations for fetuses affected by β-thal major

A

Elevated levels of Hgb F partially compensate for absence of Hgb A (though death usually occurs by 10 y/o unless tx is begun early w/ periodic blood transfusions)

54
Q

Purpose of transfusions for pts w/ β-thal major (2)

A

Severe anemia is reversed and extramedullary erythropoiesis is suppressed

55
Q

Sequelae associated w/ β-thal intermedia

A

Variable but decreased amounts of β-chains are produced, and as a result, variable amounts of Hgb A are produced

56
Q

Inheritance for Hgb S relative to β-thal

A

Usually behave as alleles (though only one gene inherited from each parent)

57
Q

Sequelae associated w/ sickle cell-β0-thal

A

No normal β-chains, and therefore no Hgb A produced

58
Q

Demographics w/ higher rates of β-thal minor (5)

A

Mediterraneans, Asians, Middle Easterners, Hispanics, West Indians

59
Q

Clinical presentation of β-thal minor

A

Asymptomatic mild anemia (though varies depending on amount of β-chain production)

60
Q

Who should be offered carrier screening for hemoglobinopathies in pregnancy?

A

All pts (w/ emphasis on high-risk Black, Southeast Asian, and Mediterranean pts)

61
Q

Hemoglobinopathy carrier screening in pregnancy lab testing (2)

A

Hgb electro, CBC

62
Q

Low-risk ethnic groups for hemoglobinopathies (5)

A

Northern Europeans, Japanese, Native Americans, Inuit/Eskimos, Koreans

63
Q

Next step if pt tests positive as carrier for hemoglobinopathy on Hgb electro

A

Partner testing

64
Q

Next step if both parents are found to be carriers for hemoglobinopathy

A

Genetic counseling

65
Q

Next step if pt is found to have anemia w/ low MCV

A

Iron studies/ferritin to r/o IDA

66
Q

MCV suggesting microcytic anemia

A

<80

67
Q

Hgb electro results for pt w/ β-thal

A

Elevated Hgb F, elevated Hgb A2 (>3.5%)

68
Q

Hgb electro results for pt w/ α-thal

A

Normal

69
Q

Testing to confirm α-thal

A

DNA-based testing

70
Q

When to test for α-thal

A

MCV is low, IDA is excluded, Hgb electro not c/w β-thal

71
Q

When to offer fetal genetic testing for α-thal and/or β-thal

A

If specific mutation/deletion is known

72
Q

Prenatal genetic testing options for thalassemias (2)

A

CVS (10-12wga), amnio (>15wga)

73
Q

Pre-pregnancy testing option for couples w/ known hemoglobinopathy or who are known to be carriers

A

PGT (most successfully done for SCD and most cases of β-thal)

74
Q

Percentage of families in whom antenatal dx confirms fetus w/ SCD who elect to continue pregnancy

A

~70%

75
Q

Increased risks in pregnancy associated w/ SCD (8)

A

sAB, PTL/PTD, PROM, antepartum hospitalization, PP infection, FGR, LBW, IUFD

76
Q

Which pregnancies are higher-risk between SCD and Hgb SC disease?

A

SCD

77
Q

Supplementation recommended for pts w/ SCD, and why

A

Folic acid supp (4mg per day), 2/2 continual turnover of RBCs

78
Q

Are C/S and/or epidural analgesia contraindicated in pts w/ SCD?

A

No (as long as care taken to avoid hypotension and hypoxemia)

79
Q

Precipitating factors that could cause vaso-occlusive crises (4)

A

Cold environment, heavy physical exertion, dehydration, stress

80
Q

Med used for tx of SCD that is contraindicated in pregnancy 2/2 teratogenicity

A

Hydroxyurea

81
Q

Important management considerations for pain crises in pregnancy (2)

A

Prompt administration of analgesia, assessment of pain/RR/sedation level

82
Q

Meds to provide for pain control during pain crisis

A

PO/IV/IM/subQ opiates

83
Q

Vital sign to watch during pain crises, and management strategy if abnormal

A

SpO2, provided supp O2 if <95%

84
Q

Specific consideration for pain crises during 3rd tri

A

Pain crises may have prolonged course, and may not resolve until PP

85
Q

General risks associated w/ blood transfusion (3)

A

Alloimmunization, viral infections, iron overload

86
Q

Major complications in SCD that may require exchange transfusion (4)

A

Worsening anemia, intrapartum hemorrhage/septicemia/C/S, pain crises, ACS

87
Q

Hct value below which pRBC transfusion is definitively indicated for SCD

A

No exact value

88
Q

Transfusion goals in SCD (2)

A

Lower Hgb S to ~40%, raise Hgb to ~10

89
Q

How to determine need for additional transfusions in pregnancy after initial transfusion

A

Serially monitoring of Hgb levels and Hgb S percentage

90
Q

Is ppx pRBC transfusion recommended?

A

No

91
Q

Fetal surveillance recs for SCD, and special consideration

A

Serial growths and ANT recommended, results interpreted w/ caution if pts having pain crises (but revert back to normal w/ resolution of episode)

92
Q

Pregnancy course for pts w/ α-thal trait

A

Not significantly altered

93
Q

Pregnancy course for pts w/ Hgb H disease

A

Favorable outcomes w/ exception of mild-mod anemia

94
Q

Pregnancy recs for pt w/ β-thal major

A

Pregnancy not recommended unless normal cardiac function who have had prolonged hypertransfusion therapy to maintain Hgb >10 and iron chelation therapy

95
Q

Med used for iron chelation therapy, and safety in pregnancy

A

Deferoxamine, not recommended in pregnancy

96
Q

Hgb minimum below which pRBC transfusion should be recommended in pts w/ β-thal major

A

10

97
Q

Fetal surveillance recs for pts w/ β-thal major

A

Serial growths, and if suboptimal add on ANT

98
Q

Pregnancy course for pts w/ β-thal minor

A

Mild asymptomatic anemia

99
Q

Is iron supp recommended in pts w/ β-thal minor?

A

Only if documented iron deficiency

100
Q

Risks associated w/ β-thal minor in pregnancy (2)

A

FGR, oligo (though no differences observed in APGAR scores, congenital malformations, perinatal mortality)

ACOG Pub Review (12 decks)

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