What happens and where does the baby go

There’s these videos on YouTube from tic whatever it is and the videos are of pregnant women sucking in their bellies.

I mean like very pregnant, like fully belly 9 months got a whole baby in there and they suck in and make their bump go away.

Okay. Ma’am. What just happened. Did the baby like get sucked into oblivion? My Unterstanding about pregnancy is that.. okay I am so confused about this anatomically. Is the baby being sucked back towards the spine? Does it feel itself being smushed by its moms stomach muscles? I didn’t know this was physically possible, for some women to suck in their 9 month pregnant uteruses and make them disappear as if we have like an extra space between the rest of our organs and our uterus (that’s not the case the other organs get smashed during pregnancy)