Heavy "breathing" on the part of pregnant females?

[aoikirin]

I've noticed sometimes that pregnant female hissers of all types sometimes sway back and forth rhythmically every eight to fifteen seconds.  The movement is very slight but if you keep your head still and watch for it you'll see it.  

Has anyone else noticed this? Is it common knowledge ?

 

[Allpet Roaches]

Yes, fat mantids and roaches are well  known for this behavior.

 

[Axolotl]

Any theories on the reason for that behavior? Does it somehow help the eggs?