When I was pregnant, Rebecca warned me that while my hair was looking all nice and shiny and plentiful, I'd lose most of it in the few months after birth.
(Rebecca's all doom and gloom isn't she, she also warned me about painful let-down reflex, and soggy breasts, and Nico's flat head, and other stuff as well...)
Anyway, I had just attributed this to either hormone fluctuation, or to my blood volume going back to normal.
Now I know that it was neither.
