Partner is pregnant, ultrasound looked cool. Had an e-ink dev board collecting dust. So here we are. Pretty simple stuff, the board is an Adafruit MagTag. And all we needed to do was have a progress bar, some graphics, and some text. There are some useful guides to making a progress bar and graphics for this e-ink board HERE and HERE.
I used some wikimedia fetal development graphics for each step. The key thing is to format the image correctly for the e-ink display. This is the ImageMagick command I used to do that:
magick convert input.png -dither FloydSteinberg -define dither:diffusion-amount=0% -remap ./eink-4gray.png BMP3:output.bmp
Have it sticking on the fridge right now, the battery consumption is really low, and only used when updating the progress, should be good for a year or more.