Okay, first off, what you've got there is a Slovak birth certificate, as evident by the Slovak national insignia on the top left, which fits the time frame, as Czechoslovakia didn't exist in 1941 and Tiso was in power in the newly created Slovak State.. The ev. a.v., as somebody already guessed is just shorthand for "Evanjelická cirkev augsburského vyznania", or "Evangelical church of the Augsburg Confession", i.e. the local Lutheran church.

Please post a scan. Is it really "er."? It could be "ev.", which stands for "evangelisch".

Additional to mare_apertums question:

Is there really a point 'religion'? Birth certificates from this time I've seen, admittedly only from within Germany itself, usually had only gaps for 'father' and 'mother' that would be filled in like, let's say 'Father: Schmidt, Franz; Blacksmith; protestant Mother: Schmidt, Irmgard née Müller; Weaver; lutheran'.

If it's the same with your certificate I would guess it means "evangelisch, arischer Rasse" = 'evangelic, of aryan race', which would make sense since it would distinguish your grandmother from 'non-aryan' slavic czechs (= 'sub-humans')