#78 Hemoglobinopathies in Pregnancy Flashcards
When is hemoglobin F present?
12-24wks gestation
What polypeptide chains make up Hemoglobin A
Two alpha and two beta chains
What polypeptide chains make up Hemoglobin F
Two alpha and two gamma chains
What polypeptide chains make up Hemoglobin A2
Two alpha and two delta chains
When does the fetus start making hemoglobin A?
Third trimester
The genes for the alpha globin chains are on which chromosome?
Chromosome 16, short arm
The gene for the beta globin chain is on which chromosome?
Chromosome 11, short arm
Inheritance pattern of sickle cell?
Autosomal recessive
What causes Hemoglobin S?
single nucleotide substitution of thymine for adenine in the beta globin gene. Causes substitution of valine for glutamic acid
What genotype(s) lead symptomatic sickle cell?
Hemoglobin SS
Hemoglobin S/beta thalassemia
Hemoglobin SC
How common is sickle cell trait, sickle cell disease, sickle cell anemia in the African American population?
1 in 12 Sickle Cell trait
1 in 300 sickle cell disease
1 in 600 sickle cell anemia (Hgb SS)
What is the most significant threat to patient’s with sickle cell disease?
Acute chest syndrom
What is acute chest syndrome?
Pulmonary infiltrate with fever that leads to hypoxemia and acidosis caused by vasoocclusion from sickling or embolization of marrow from long bones by sickling
How many copies of the alpha gene are there?
Four
What are the different kinds of alpha thalassemia?
a-/aa = clinically unrecognizable, normal lab testing a-/a- = alpha trait, microcytic anemia. Trans deletion aa/-- = alpha trait, microcytic anemia. Cis deletion a-/-- = Hemoglobin H disease, hemolytic anemia --/-- = hemoglobin bart's disease, hydrops fetalis
What outcomes are associated with hemoglobin Bart (alpha-thal major)?
Hydrops fetalis, IUFD, preeclampsia
How does beta-thalassemia minor present?
Asymptomatic mild anemia
How does beta-thalassemia major present?
Severe anemia with resultant extramedullary erythropoesis, delayed sexual development, and poor growth. Death usually by age 10 unless treatment is begun early with periodic blood transfusions.
Who should be screened for hemoglobinopathies?
All patient’s of African descent should get hemoglobin electrophoresis.
Patient’s of Southeast Asian or Mediterranean descent should get CBC, if microcytic anemia (w/ normal iron studies), should get hemoglobin electrophoresis, if electrophoresis normal should evaluate for alpha thalassemia
How do you test a patient for alpha-thalassemia trait?
Molecular genetic testing. Hemoglobin elecrophoresis nor solubility testing can identify alpha-thal trait.
What obstetric complications are associated with Hb SS (maternal and fetal)?
Preterm labor, PROM, antepartum hospitalization, postpartum infection, IUGR, low birth weight, preterm delivery. Also at increased risk for SAB and IUFD.
Hb SC also at risk for these, but to a lesser extent
How much folate should paitent’s with sickle cell disease take prenatally?
4mg folic acid daily, due to continual turnover of red blood cells.
What are precipitating factors for painful crisis in sickle cell?
Cold environment, heavy physical exertion, dehydration, and stress
What is the goal Hb S % and total hemoglobin level after transfusion?
40%, 10g/dL
How do you manage pregnancy in patient’s with beta-thal major?
Pregnancy only recommended for patient’s with normal cardiac function, hemoglobin at 10g/dL and iron chelation therapy with deferoxamine.
Maintain hemoglobin at 10g/dL during pregnancy with transfusions. Deferoxamine not continued during pregnancy since safety not established in pregnancy. Serial growth scans, initiate fetal surveillance if growth suboptimal.
