Why are human females rarely haemophilic?

Explanation

Haemophilia is a X-linked recessive disease characterised by the inability to form blood clots. The human female having haemophilic allele on single X-chromosome does not produce haemophilic phenotype. Either the mother of such female has to be at least carrier or the father should be haemophilic. Haemophilics human females are rare because it requires two defective X-chromosomes for haemophilic condition to be produced in females. Such a case may arise only when the father is haemophilic and the mother is either heterozygous or homozygous for the haemophilic gene. Such females generally die before birth or before reaching adolescene. due to severe bleeding. Thus, chances of homozygous girl being born in random mating are very rare.