Avoid pregnancy, this mechanic is critically bugged. Although perhaps NPCs getting pregnant is not dangerously bugged. Read on.
Confirmed problem scenario: If you play a female character and get impregnated by an NPC, a quest will initiate that causes some stats to go up then down. Programming for this is very sloppy -- a quest boosts stats upwards with scripts that operate once during its stages, and the game's baseline pregnancy mechanics have scripts that lower stats downwards when pregnancy is done. See the problem yet?
The quest only works once, the very first time. The stat reducing scripts apply every time. Which means every time after the first pregnancy, your stats only go down. So low that your melee attack damage will go into the negatives.
Possible problem scenario: the same pregnancy message also plays when female NPCs give birth. I didn't test if the pregnancy script negates stats from the player even then or if stat decreases apply to NPCs like they do the player. Maybe NPC pregnancy is safe, but if an NPC does get stat decreases and has to get into combat later, this could be an issue.
In short, avoid pregnancy! You have to go to a special location to enable pregnancy mechanics so they're not on by default. Do not enable player pregnancy. Be cautious about NPC pregnancy.
