Haemophilia A is a severe bleeding disorder caused by a deficiency in clotting factor VIII (FVIII). It is an X-linked recessive bleeding disorder affecting one in 10,000 males. Prevalence of the haemophilia gene in the general population has increased recently due to advances in treatment, which has resulted in reproductive fitness among heamophiliacs. Patients suffering from this disease and their families are faced with problems relating to morbidity and mortality from the disease. These include a continual risk of uncontrolled bleeding, haemarthroses and subsequent arthropathy and above all, the genetic risk to progeny. Factor VIII gene is very large with 26 exons. Defects in this gene result in the deficiency of FVIII molecule. With the advent of recent advances in the molecular biology, it is possible to identify the multiple molecular defects such as point mutations, premature stop codons, deletions, and inversions etc in the FVIII gene in patients with haemophilia. Nowadays the use of polymerase chain reaction (PCR)-based linkage analysis and direct mutation detection in the chorionic villus sample obtained at 10-12 weeks of gestation has significantly improved the prenatal diagnosis of haemophilia.