#78 Hemoglobinopathies in Pregnancy

Question 1

When is hemoglobin F present?

Answer 1

12-24wks gestation

Question 2

What polypeptide chains make up Hemoglobin A

Answer 2

Two alpha and two beta chains

Question 3

What polypeptide chains make up Hemoglobin F

Answer 3

Two alpha and two gamma chains

Question 4

What polypeptide chains make up Hemoglobin A2

Answer 4

Two alpha and two delta chains

Question 5

When does the fetus start making hemoglobin A?

Answer 5

Third trimester

Question 6

The genes for the alpha globin chains are on which chromosome?

Answer 6

Chromosome 16, short arm

Question 7

The gene for the beta globin chain is on which chromosome?

Answer 7

Chromosome 11, short arm

Question 8

Inheritance pattern of sickle cell?

Answer 8

Autosomal recessive

Question 9

What causes Hemoglobin S?

Answer 9

single nucleotide substitution of thymine for adenine in the beta globin gene. Causes substitution of valine for glutamic acid

Question 10

What genotype(s) lead symptomatic sickle cell?

Answer 10

Hemoglobin SS
Hemoglobin S/beta thalassemia
Hemoglobin SC

Question 11

How common is sickle cell trait, sickle cell disease, sickle cell anemia in the African American population?

Answer 11

1 in 12 Sickle Cell trait
1 in 300 sickle cell disease
1 in 600 sickle cell anemia (Hgb SS)

Question 12

What is the most significant threat to patient’s with sickle cell disease?

Answer 12

Acute chest syndrom

Question 13

What is acute chest syndrome?

Answer 13

Pulmonary infiltrate with fever that leads to hypoxemia and acidosis caused by vasoocclusion from sickling or embolization of marrow from long bones by sickling

Question 14

How many copies of the alpha gene are there?

Answer 14

Four

Question 15

What are the different kinds of alpha thalassemia?

Answer 15

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

Question 16

What outcomes are associated with hemoglobin Bart (alpha-thal major)?

Answer 16

Hydrops fetalis, IUFD, preeclampsia

Question 17

How does beta-thalassemia minor present?

Answer 17

Asymptomatic mild anemia

Question 18

How does beta-thalassemia major present?

Answer 18

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.

Question 19

Who should be screened for hemoglobinopathies?

Answer 19

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

Question 20

How do you test a patient for alpha-thalassemia trait?

Answer 20

Molecular genetic testing. Hemoglobin elecrophoresis nor solubility testing can identify alpha-thal trait.

Question 21

What obstetric complications are associated with Hb SS (maternal and fetal)?

Answer 21

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

Question 22

How much folate should paitent’s with sickle cell disease take prenatally?

Answer 22

4mg folic acid daily, due to continual turnover of red blood cells.

Question 23

What are precipitating factors for painful crisis in sickle cell?

Answer 23

Cold environment, heavy physical exertion, dehydration, and stress

Question 24

What is the goal Hb S % and total hemoglobin level after transfusion?

Answer 24

40%, 10g/dL

Question 25

How do you manage pregnancy in patient’s with beta-thal major?

Answer 25

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.