While parasitic ovoviviparity explains rahn (and possibly Queen of the Deep) pregnancies, it's also kind of the opposite of what this thread was made to speculate upon: non-parasitic pregnancies (or at least, as close to non-parasitic as they can get) that end in eggs being laid when the mother's species doesn't naturally lay eggs.
I know, I was answering to the post above mine - should've clarified
For the rest, biology nerd theory incoming:
The main differences between egg-laying and non egg-laying species are:
- whether the embryo's placenta attaches to the uterin wall
- where the embryo gets the nutrients necessary for its survival/development (the mother's blood, the egg's yolk, or something in between, like substances secreted by the uterus)
Essentially, the placenta is everything, bc it's the organ that manages ALL the exchanges between the embryo and its environment. The umbilical cord connects to the mother indirectly through the placenta.
And since the placenta is a structure that's made from the embryo's cells, what it does is determined entirely by the embryo's genes
For hard-shelled eggs, a non-egg-laying mother species would need to get themselves wholeass new organs (because a hard shell isn't gonna make itself)
But then microsurgeons are space magic, so i don't see why they couldn't modify the pregnant individual to have the new necessary organs, or even build the egg's shell themselves, if they also monitor the embryo's genes to ensure that the pregnancy carries to term
There's also the issue of whether the contractions would break the eggs duting birth/laying, but since the PC's vagina can gape wider than most TV screens are large, I don't think there's gonna be a problem there
For soft-shelled eggs, I don't think the mother's species would require that many alterations - the placenta would simply never attach to the mother's uterin wall, instead sustaining the embryo on uterin secretions or the egg yolk (which is essentially an overgrown ovule with carbs and lipids inside it)
TBH, the fact that so many alien species are compatible and use the same molecules to store genetic information at all breaks my suspension of disbelief way more than a mammal laying eggs
(but then if all life in the universe was born from horny precursors, that explains everything lol)