The Pregnancy is just a single image at the end of the game after you hit 40 Acts.
I don't think the game was fully finished after releasr, so the missing animations could have been saved for the Hostess but the update never happened.
The image (one per each girl, all of them attached below) appears at the score screen at the end of the game if you managed to get them knocked up. All animations are in the game and available, but for whatever reason you get 48 of them while the counter seems to imply it's "out of 40". I think there's even a ding/chime if you get to 48, letting you know there's nothing more to find.
If you want to get all 48, you gotta remember that each character has foreplay and penetration (depending on how close their are to climax) animations in sub and dom versions (depending on who initiates the act) for each possible pairing. Then there's a 2nd set of animations for the hot springs, which follows mostly the same rules. Also, if you open up the Gallery (there's two of them in the menu, one for hot spring, one for room sex) you can press H and move around with arrows to uncover any animations you've missed. Sadly, as there's no way to save the game mid-run, it can't be used to keep track of the animations that you still need to get. All that said, there's no reward for high score and/or perfect run, as far as I know, so there's no need to sweat it.
Edit:
If you are struggling with getting enough points to have everyone bonk everyone enough times to unlock everything and you don't want to use the cheat mode with infinite points, it helps to do all the optional stuff early on:
- order a feast for each room, consume it, and then have the innkeeper set up the rooms to sleep. Careful not to go to sleep on all of the characters at once, as that ends the run. You can easily wake them all up as long as you have at least one awake.
- drink all the stuff you can out of the vending machine for each character (some drinks have effects that can be used to your advantage, one is arguably bad for you and all give bonus score). It seems you can only interact with the machine if you are dressed in the robes. Some characters can drink multiple times, but the limit doesn't seem to replenish once you reach it.
- uncovering new positions and simultaneous climaxes are both worth a lot of points
- you get points for undressing and entering the water for the first time (can make it happen like twice or thrice for one of the girls as her choice of drink from the vending machine causes her to revert back to the initial state before unlocking the sex interaction)
- not 100% sure what triggers it, but sometimes there's big snowflakes coming down among the usual snow dots and you can fly into them with the god (the blue elephant thing) for more points
- also, while it's probably obvious, the ideal "breeding" pair exists for each character, with a matching number of interactions before climax needed, and it's obviously not their spouse/girlfriend, since you only lose the act points when the male cums. Not a big fan of forcing your choices, but following those pairings is the easiest way forward and if you do it right, you get enough points left over to have all the girls knocked up and try all the poses with the other men as well