A Stuck Pregnancy refers to a situation in any of the Creatures games where a female creature is physically unable to lay her egg. While not immediately life threatening, it may make the female creature tired or hungry due to the fact the egg takes up a portion of her energy.
The main culprit behind stuck pregnancies is a genetic mutation where the female Creature doesn't produce progesterone during her pregnancy, causing the egg to remain inside her uterus indefinitely unless the player takes action. A good indicator of this mutation in C3/DS is when a female creature gets pregnant but her belly stays flat.
In most cases, the female Creature can be coaxed to lay her egg by giving her a large shot of progesterone. In some rare cases, however, a progesterone injection won't work due to the female's egg-laying receptor mutating, or because her uterus is damaged. This can only be fixed via a third-party COB such as the C-Section available at Norntropolis for Creatures and the Eggernator for C3/DS (No known tool exists for Creatures 2). The player can also use the CAOS Code (C3/DS Only), targ norn mesg writ targ 65 to induce a birth.