Prenatal Diagnosis of Homozygous Alpha-Thalassemia-1 of Southeast Asian Type by Polymerase Chain Reaction

Abstract

Abstract: The association of Hemoglobin Bar's (Hb Bar's) hydrops fetalis or homozygous alpha-thalssemia of Southeast
Asian type is very common in Southeast Asia especially in Thailand. Becaues of the fact that the pregnancy may be complicated by toxemia , ante-or post-partum hemorrhage as well as peychological burden for the family and the mother who have to cary a nonviable fetus to term. The prenatal diagnosis of Hb Bart's hydrops is therefore justified so that the family can be given a choice of early termination of the pregnancy. In order to idenify the presence of Hb Bart's hydrops in the fetus, the collaboration study in 18 high risk pregnancies with Hib Bar's hydrops fetalis were undertaken between February 1993 and October 1996 at Obstetrics and
Gynecology Department and the Hematology Division, Depatment of Pediatrics, Pramongkutklao Hospital and College of Medicine, Bangkok, Thailand. Amniocentesis was done at 16-33 weeks of gestation. DNA analysis were performed by polymerase chain reaction (PCR) using 2 techniques, 1) three nucleatide primers and 2) four nucleotide primers. After either therapeutic abortion or birth, heart blood or cord blood was drawn to confirm diagnosis by Hb electroresis and DNA analysis. Of 18 high risk fetuses, 6 were recognized as Hb Bart's hydrops fetalis, 7 showed the alpha-1 trait, 1 showed alpha thai-2 trait and 4 were normal fetus. The technique was entrely suitable for pretal dagnosis of Hb Bart's hydrops fetalis. This technique was rapid, simple non-radioactive method, less expensive and avablable in most PCR laboratories.