Help with SQL date conversion

I have a column named birth_date which is varchar(8).  I am trying to convert this to a date and keep getting:

Msg 241, Level 16, State 1, Line 1
Conversion failed when converting date and/or time from character string.

The data in the column is formatted as 01011997.

I thought this would work, but it does not and I'm not sure why:
convert(date,birth_date,101)

Any help appreciated!