Whether it's a mouse, rat or ASF - if it's in active delivery of the litter just let her do her job without too much fussing from you. Especially the first time momma's can get a bit stressed if you hang about watching too closely (some could care less though LOL).

They will lick and chew at the baby to remove the cord and eat the afterbirth (it's good for the mom). They will lick and grab/mouth the baby. They are stimulating it to breath and moving it out of the way while they pop out the rest. Some new momma rats will be confused at what the heck is falling out their butt end and grab a pink and run about with it for a minute. They eventually figure it out though I've had to wait till she's done and settled and nudge one of those pinks back in with the rest.