Management of Alpha Thalassemia HbH Disease in Pregnancy
Pregnant women with HbH disease require close monitoring with CBC every 3-6 months to assess for worsening hemolytic anemia and determine transfusion needs, with particular attention to maintaining adequate hemoglobin levels for optimal fetal growth. 1
Pre-Pregnancy Counseling and Risk Assessment
- Genetic counseling is essential before conception to discuss the 25% risk of severe disease (Hemoglobin Bart's hydrops fetalis) if the partner is also a carrier, which is typically fatal. 2
- Partner screening is mandatory when a woman with HbH disease plans pregnancy, including CBC with MCV measurement, and if MCV <80 fL, proceed with hemoglobin analysis and DNA testing. 2
- Prenatal diagnosis options should be discussed, including chorionic villus sampling at 10-13 weeks or amniocentesis at 15-20 weeks for DNA-based testing. 2
Hematologic Monitoring During Pregnancy
- Monitor CBC every 3-6 months throughout pregnancy to assess the degree of hemolytic anemia, as HbH disease severity can vary significantly. 1
- The hemoglobin target should be maintained at approximately 10 g/dL to ensure optimal fetal growth, though transfusion needs vary based on baseline severity. 3, 4
- Iron supplementation requires careful consideration: While pregnant women with alpha-thalassemia silent or minor genotypes have a 40-84% incidence of concurrent iron deficiency, those with HbH disease (3-gene deletion) rarely develop iron deficiency. 5
- Measure serum ferritin to exclude concurrent iron deficiency before initiating iron supplementation, as inappropriate iron supplementation in HbH disease can worsen hemosiderosis. 2, 5
Transfusion Management
- Intermittent transfusion therapy may be required, especially during intercurrent illness or if hemoglobin drops significantly below baseline. 6
- The severity of HbH disease varies based on mutation type (deletional forms are milder than non-deletional), which influences transfusion requirements during pregnancy. 4
- Non-deletional HbH disease may require more aggressive transfusion support due to moderate to severe anemia with ineffective erythropoiesis. 4
Fetal Surveillance
- Ultrasound surveillance in the late second and early third trimester is critical to detect hydrops fetalis if the fetus has inherited severe alpha thalassemia. 2
- Middle cerebral artery Doppler should be used to assess for fetal anemia in cases of suspected hydrops fetalis. 1
- Monthly fetal growth monitoring scans from viability are recommended to ensure adequate fetal development. 7
Obstetric Complications to Monitor
- Increased risk of gestational diabetes, preeclampsia, and hypertension should be anticipated, similar to other thalassemia syndromes. 7
- Spontaneous miscarriage and fetal loss occur in 9-33.3% of pregnancies in women with thalassemia. 7
- Preterm births occur at increased rates due to underlying maternal or obstetric complications. 7
Thromboembolism Prophylaxis
- Prophylaxis with heparin or low-molecular-weight heparin is indicated, particularly if the patient has undergone splenectomy, as this significantly increases thrombotic risk. 7
Delivery Planning
- Cesarean delivery rates are higher (24-100%) due to fetopelvic disproportion, osteoporosis, or maternal complications. 7
- Pregnancies should be managed in expert centers with a multidisciplinary team including hematology, maternal-fetal medicine, and neonatology due to increased maternal and fetal risks. 7
Critical Pitfalls to Avoid
- Do not routinely supplement iron without confirming iron deficiency with ferritin testing, as HbH disease patients develop hemosiderosis from increased iron absorption and potential transfusions. 5, 4
- Failure to screen the partner for thalassemia carrier status can result in missed diagnosis of at-risk pregnancies for Hemoglobin Bart's hydrops fetalis. 2
- Delayed recognition of worsening anemia during pregnancy can compromise both maternal and fetal outcomes—maintain regular CBC monitoring. 1