When does first heat usually occur

Jaiylah18

Hello I have two bull terrier puppies they are sisters. They will be 9 months on the 8th of February.  They have not had their first heat yet.  I was just wondering around what age does the first heat usually occur.  I just wanted to make sure that there was nothing to be concerned about.  

Jbird

Mine went on her first heat at 10 months.

AmyJo

My Ella started hers January 3 @ 10 months and she is still bleeding.

I think it's winding down.

Jbird

Terra started New Year's Day and ended around Jan 20th.

Jbird

But 1 week prior she became quite swollen but no blood until New Years.

BulliesofNC

http://www.bullterrierfun.com/dog-heat-cycle/