Salem wrote:
I learned something new today, I didn't know animals gestation period was based on their complexity.
Heh. They're not; that's just the usual human-centered doctrine claiming that, among other things, we're more complex than all those lesser creatures. We're not actually, except for one major organ that is a bit overdeveloped in our species. Other than that one big lump of nerve tissue, we're about the same complexity as any other mammal.
If you google for "gestation period", you'll find a lot on the topic. The main things correllated with gestation period are body size and stage of development at birth. Humans are one of the larger creatures in our world, which gives us a relatively long gestation period. Horses, rhinoceroses and elephants have even longer gestations.
OTOH, we are born somewhat prematurely, which decreases our gestation period a bit. The problem is our big skulls, combined with the biological accident that birth requires passing through a ring of bone. This is why human birth is so difficult; we're born at the latest stage in which our skulls can fit through that bony ring. Sometimes the fetus and mother don't coordinate this quite right, and they both die, or at least did before Caesarean delivery became practical. This put selection pressure on our ancestors for premature birth.
Anyway, if you look at the heads and hips of the keidran we've seen, they probably have similar problems. They're about our size, with heads and hips about the same size as ours, so you'd expect pregnancies about the same length. And similar birthing problems.
OTOH, in our world, the Carnivora do have gestation periods that are a bit shorter than what you'd expect from an animal their size. Lions and tigers have gestation periods around 100-120 days, less than half ours. If the keidran are like our cats, we can expect the same gestation for them.
But it's really all up to Tom. The model animals in our world give him a fair amount of leeway in such things. Keidran could be born even more immature than humans, with a longer nursing period. And for a human-keidran hybrid, anything from around 90 to 270 days would be credible. He'll pick a length that's good for the story line.