In Southeast Asia, Hb Bart's - a thalassemia major is the most common cause of Hydrop Fetalis. Aim: Screening for a° thalassemia carrier and prenatal diagnosis for Hb Bart's for couples affected with Hydrop Fetalis. Meterials and Methods: 12 couples affected with Hydrop Fetalis were screening by MCV, MCH, DNA analysis and erenatal diagnosis for Hb Bart's. Results: 100 percent of them are heterozygote of (~SEA/aa). Prenatal diagnosis for 9 pregnants: 5 fetus were diagnosed by DNA testing of aminotic fluids (4 fetus were affected with Hb Bart's, 1 fetus was carrier of (~SEA/aa). 4 fetus were confirmed by DNA testing of cord blood at birth was affected with Hb Bart's. Conclusion: Screening for couples at risk and prenatal diagnosis for Hb Bart's play an importan role for genetics counselling and prevention of this disorder.