How common is hemophilia?  

1:10,000 males. Hemophillia a in about 1:10, 000 males and hemophilia b in about 1:20, 000 males. It is less common in females.
A or B? Hemophilia a is the most common type of the condition; 1 in 4, 000 to 1 in 5, 000 males worldwide are born with this disorder. Hemophilia b occurs in approximately 1 in 20, 000 newborn males worldwide.