Current release info is here:
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Subject to change ofc, can't release it if it isn't done. But I am working very hard on it atm.
Zombies and beasts can't impregnate yet due to "dead" or "species incompatible" sperm, this is a story related plot device that will be resolved towards the end of the game's 1st ACT during the main story. The gestation time will be the same as for human offspring, which is now 3 days for Tiffany after she gets captured and injected with the Fertility Enhancement Serum in the Casino basement.
You won't need a patch, you'll be able to enhance and grow all of the girls' assets in-game over time through their pregnancies! ;P