When I first started out I had guppies and I got rid of them cause they bred out of control but I never had to take out the pregnant females cause I found that none of them every ate the fry which is why they bred out of control
+1fluttermoth said:It's really not common for female livebearars to die after giving birth
These fish really need warm, clean water and decent filtration. Bigger tanks and plenty of live plants would help things along no end.