Prenatal Diagnosis of a-Thalassemia-! (SEA type) by Chorionic Villus Sampling
PHARUHAS CHANPRAPAPH, M.D.*, THEERA TONGSONG, M.D.*, CHANANE WANAPIRAK, M.D.*, SUPATTRA SIRICHOTIYAKUL, M.D.*, TORPONG SANGUANSERMSRI, M.D.**
Affiliation : * Department of Obstetrics and Gynecology, **Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
Objective : To describe the experience of prenatal diagnosis for Hb Bart's disease, by chorionic villus sampling (CVS) with DNA analysis.
Design : Descriptive study Settings : Department of Obstetrics and Gynecology, Faculty of Medicine, Chiang Mai University.
Subjects : Sixteen high risk pregnancies at risk of Hb Bart's disease who were eligible for CVS criteria between 1 January, 1999 and May 31, 2000.
Materials and Methods : Fetal villi were obtained by either transcervical (TC) or transabdo minal (TA) CVS route to extract DNA and detect for a.-thal-1 gene deletion (SEA type) with modi fied Chang's method. The CVS results were confirmed by either serial ultrasound or cordocentesis or diagnosis after pregnancy termination.
Main outcome measures : The efficacy, safety and pregnancy outcomes.
Results : CVS was successfully done in all of 16 cases (5 with TC and 11 with T A), The mean gestational age was 13.25 ± 2.9 weeks. The procedure time for TA was shorter than that of TC (4 .64 ± 5.4 vs 10.4 ± 11.3 min). The CVS result showed as follows: 3 normal fetuses, 7 a.-thal-1 carriers, 4 fetal Hb Bart's, 1 misdiagnosis and 1 failure to diagnosis due to technical error. The sen sitivity and specificity were 100 per cent (4/4) and 90.91 per cent (10/11), respectively. One case of Hb Bart's misdiagnosis and one failure case were later confirmed for a.-thal-1 trait and a.-thal-11 Hb E trait by cordocentesis, respectively. The pregnancy outcomes included 11 livebirths, 4 termi nated cases and 1 fetal loss of continuing pregnancies. No serious complications occurred.
Conclusion : This preliminary experience suggests that CVS is an effective method for early prenatal diagnosis of fetal Hb Bart's.
Keywords : Prenatal Diagnosis, Chorionic Villus Sampling, Thalassemia, a.-Thalassemia-! (SEA Type), Hb Bart's, Pregnancy Outcome
