'Sucking pad' is the common term for the "swollen" cheeks found in young infants. The technical term is corpus adiposum buccae, but even doctors don't use that -- not even when publishing papers for other doctors. The Latin term does give us a more specific definition, however: "the fat body of the cheeks". And that's exactly what they are -- pouches of fatty tissue found in the cheeks of newborn babies. Infants also have a similar swelling of the lips, which may also be referred to as sucking pads; in this case they are formed by swelling (edema) in the tissue of the lips.
A baby's mouth is different from yours and mine. First of all, it's still developing, so certain things aren't in their final resting places yet. But more importantly, it is focused on one primary function: sucking. As adults we will need room for our teeth to chew, and our tongue to move all over the oral cavity to allow chewing and speech. But for an infant speech and chewing won't come for a while, so a baby is born with a number of modifications that help it suckle better than an adult ever could. Infants are born with a complete lack of teeth and a tongue proportionately larger than the rest of the mouth. The unneeded space in the cheeks is filled by the sucking pads. These modifications (among others) take up a lot of the extra space in the oral cavity that would interfere with with the air-seal needed for effective sucking. The sucking pads of the lips help form a better seal between the lips and the nipple.
The sucking pads of the cheeks are stuck between the masseter muscle and the buccinator muscle, where they stabilize the cheeks and jaw, and fill the buccal cavity. They will start to disappear on their own as the infant's mouth develops, and they are usually gone by 4 to 6 months of age.
These pads are so important that even if the baby is undernourished or sick they do not waste away as the body starts processing body fat for energy. If the pads are damaged or deformed and the baby cannot feed it is a potentially serious condition, and will require special feeding and most likely clinical intervention. If your baby is not able to feed fully and easily, this may be a sign that the sucking pads aren't healthy. If your child has any feeding problems you should seek guidance from your pediatrician or other trained professional.
momomom says re Sucking pads: One of the big challenges for a preterm baby is the sucking pads are not yet developed.
Thanks to momomom for correcting my errors!
Sucking pads have nothing to do with sucking blisters. Blisters on the lips resulting from feeding are not healthy, although they are not that uncommon, and are not dangerous if the baby is feeding well.