This article from Pregnancy.com/Australia explains why humans have a much harder time at labor than other animals. It's not only the bend in a woman's birth canal, writes Sarah Buckley. It's more because we don't follow our instincts. These are the same instincts that cause your cat to have her kittens in a safe, quiet place -- and they're driven by the same neurochemicals.
All mammals seek a safe place to give birth. This “nesting” instinct may be due to an increase in levels of prolactin, which is sometimes referred to as the nesting hormone. At this stage, as you may have observed with your cat, interference which the nest- or more importantly with the feeling of safety- will stall the beginning of labour.
Even after labour has started, there are certain conditions that will slow, or even stop the process. If the fight-or-flight hormones are activated by feelings of fear or danger, contractions will slow down. Our mammalian bodies are designed to give birth in the wilds, where it is an advantage to postpone labour when there is danger, and to seek safety.
Buckley is author of "Gentle Birth, Gentle Mothering."