My pregnant guppies keep dieing, help?

[bleeding heart]

Hi, my pregnant guppies keep dieing, i dont know what i am doing wrong. The seem perfectly healthy, they are eating fine, and look ready to give birth, but when the start to give birth they die within a few hours, the only thing that dont look right on them is they always have an open mouth when they die.
I cant work this out, anyone got any advice?:confused:

[~Erik3.8.07~]

what are your tank perameters?

[country_boy454]

I had that problem for a while too. Till i figured out that the males were stressing them out by trying to get some while they were giving birth. I ended up moving the females into a breeder net/box.