Idun`s pregnant?

Is Idun s fertility skill viewed as a negative or positive action? To encourage fertility to take place I should increase or decrease luck?

Luck does not change anything for Idun. The fertility is about life in general and gives creeps revive. It treats the creeps in her range as if they had revive. The chance for creeps to revive does not depend on any tower's luck. It's 50% chance, which on average means there are twice as many creeps to kill.