So here's what I've found out from some testing values:
Timinatha/Helga/Mabel/Cream/Ray all have 3 minimum pregnancies. One with the Player, One with Giants, and others respective of who they hang with at the orphanage.
Cream/Helga/Mabel appear to have the most fleshed out pregnancy content, with the ability to become hyper pregnant. Most of that is locked into the Giant Pregnancies, however Mabel can do normal with fertile gels. (When you explore with her and dipper,go upstairs repeatedly).
Give Ray a Strange egg and you can be impregnanted with his kids too.
Lilo has alot of pregnancy content in Hawaii, but is a little borked when she is really pregnant with Giant Clones. Save regularly with that.
Lila and Malons pregnancy is standard, with no real Variance, though Lila's litter seems to be related to the players virility.
Malons kids can get pregnant with all sorts of stuff, including elephants, but it does seem to be a little broken with tracking that.
Theres a bunch of other values in data relating to other pregnancies and locations, but I can't track these down or trigger them. Post too long. Click here to view the full text.