Fetal Anemia Causing Hydrops Fetalis From an Alpha-Globin Variant: Homozygous Hemoglobin Constant Spring.

BACKGROUND

Fetal anemia is often assumed to be due to red cell alloimmunization and Parvovirus infection, and can lead to hydrops fetalis and death in utero. Other causes, such as mutations of hemoglobin alpha, are less commonly considered.

METHODS

We report 7 cases with fetal anemia causing hydrops fetalis. Serial Doppler ultrasound for measurement peak systolic velocity (PSV) of middle cerebral artery (MCA) was used for evaluation of fetal anemia. Fetal anemia is suggested if the MCA/PSV ratio is >1.5 multiple of median. Cordocentesis was performed subsequently to find the cause of fetal anemia and check fetal hemoglobin for consideration of intrauterine infusion. Investigations for fetal anemia include complete blood count, blood morphology, and blood group of mother and fetus, reticulocyte counts, red cell indices, screening for thalassemia, hemoglobin typing, acid elution test, parvovirus B 19 serology, and TORCH titer (toxoplasmosis, rubella, cytomegalovirus, herpes simplex virus, human immunodeficiency virus, and syphilis). Intrauterine infusion, using irradiated prestorage filtered red cell with hematocrit level of 80%, is indicated if fetal hemoglobin is <10 g/dL.

RESULTS

Seven cases with fetal anemia were prenatally diagnosed from gestational ages 20 to 34 weeks. Initial hematocrit in these cases varied from 9% to 17.2%. In each case, causes of anemia were determined using the investigations listed above. All cases underwent uneventfully up to 3 intrauterine transfusions. DNA study for thalassemia demonstrated homozygous Constant Spring (CS) in 5 cases, homozygous CS with heterozygous E in 1 case, and compound heterozygous CS and Pakse in 1 case. The perinatal outcomes were normal term in 5 cases, preterm in 2 cases. Low birth weight was determined in 2 cases. The screening for thalassemia major, including the osmotic fragility and dichlorophenol indophenol precipitation test (DCIP), is not helpful for detecting hemoglobin variants such as Constant Spring or Pakse.

CONCLUSIONS

This study emphasizes homozygous Constant Spring and compound heterozygous CS and Pakse as a cause of hydrops fetalis. Proper management for the fetus after diagnosis can lead to a good fetal outcome. Prevention control programs should include screening of parents for the heterozygous state.