If your playing the Cult, and you receive a free Brood Pit at each base upon discovery of Centauri Genetics. If you already have a Children's Creche, are the effects of the Brood Pit additive, or does it not have any effect, because you already are receiving the effect of the Children's Creche?????
I'll try and take a stab at this, I think that the Brood Pit acts as a Children's Creche concerning the negative morale modifiers for native life as well as giving a bonus to the police effects in a base.
The regular Children's Creche negates the negative morale modifiers for regular units while the unit is still in your territoy and I believe that it also gives a +1 to morale as well as raise efficency and growth in the base by +2.