Had two "twin" children (one is human and happened spontaneously for no reason (didn't eat anything nor had any encounters until then), the second was from a tentacle egg and was added later, but both were born at the same time). I tried to remain consistent in having the two children on my arms to make sure I wouldn't just abandon two newborns in the middle of the forest, but got distracted with eating fruit and they disappeared (Got attacked by tentacles that restrained my arms with no mention of my children, then the game wouldn't accept any input of me trying to find them), tried everything to make the game mention them again, then when it did I was doing everything for my character to find them, even trying to negotiate with tentacles in exchange of my body. Anyways, by the time I found the two children and was away from tentacle danger, I was like the image shows.
The breasts never stopped growing after I started feeding them, the belly started growing after they went missing (I ate some fruit in the meanwhile cause the game never stopped making me impulsively take a bite whenever I tried to explore a new area), but the pregnant belly was mostly after I found them, as I was restrained by a tentacle and once again gave myself in exchange of having my two children back. It grew one unit every interaction I did, I guess, cause I just looked away for a bit and it was that big...
Anyways, cool game. The saves are a bit weird sometimes, though, but I was playing the first release. Would maybe recommend trying to put a way to retry the AI's imput, as it can get things wrong or deviate the plot easily, for example if you rest while being held by tentacles only to wake up free like it never happened, or the many times I was pregnant and mentioning it was enough for the AI to assume I just gave birth.