••• Chapter 14^ Management of Medical and Surgical Conditions in Pregnancy^151
❍ What ethnic groups are at higher risk of hemoglobinopathies?
African, Southeast Asian, and Mediterranean.
❍ What is hemoglobin S and hemoglobin C?
Hemoglobin S is a tetramer of 2 normal alpha chains and two beta chains with a single mutation of valine for
glutamic acid at codon 6. Hemoglobin C has a substitution of lysine for glutamic acid at the same position.
❍ What is the inheritance pattern of sickle cell disease?
Autosomal recessive.
❍ What is the prevalence of sickle cell trait in people of African origin?
1:12 African Americans have sickle cell trait. 1:40 are heterozygous for hemoglobin C.
❍ What obstetric complications occur in pregnant women with sickle cell disease?
Renal failure, gestational hypertension, and fetal growth restriction.
❍ What is the recommended dose of folic acid supplementation for patients with sickle cell disease?
4 mg per day.
❍ What is acute chest syndrome?
Pleuritic chest pain, fever, cough, hypoxia, and pulmonary infiltrate in a patient with sickle cell disease that may be
caused by infection, infarction, atelectasis, or fat embolism.
❍ What fetal monitoring is recommended for women with sickle cell disease?
Serial ultrasounds for growth as well as antenatal testing.
❍ What are thalassemias?
Impaired production of normal hemoglobin chains.
❍ How many alpha globin genes are there?
Four.
❍ How is alpha thalassemia diagnosed?
By genetic testing only, it cannot be diagnosed on hemoglobin electrophoresis. The diagnosis should be considered
in women with microcytic anemia who are not iron deficient and do not have beta thalassemia.
❍ What is hemoglobin Bart?
A tetramer of four gamma chains that is moderately insoluble and accumulates in red cells. It has a high oxygen
affinity and sequesters oxygen, leaving little to be delivered to tissues.
❍ What are the two forms of alpha thalassemia minor, and which is potentially worse for inheritance?
Alpha thalassemia minor is deletion of two out of the four alpha globin genes. These can be on the same (cis) or
opposite (trans) chromosomes. If both parents have the cis-form, there is a 50% risk of alpha thalassemia major.