Take a peek at this baby's chin, I wouldn't be surprised if it is
recessed and the baby's normal mouth position is upper lip totally
enclosing the lower lip when the mouth is closed.  Sucking the lower lip
in seems to increase stability in these kids.  Try extending the baby's
head as she comes to breast, so the lower lip touches the breast first,
this might equalize the jaw contact better, and allow more normal
sucking.
        If the chin is not recessed, or the lower jaw unusually small
(microgenia or micrognathia); look for a low tone tongue.  This baby may
be compensating for poor tongue tone, strength or mobility by using her
lips and jaw instead.  Sucking the lower lip in allows it to be pressed
against the breast with more strength than if it were flanged.  This is
why we encourage flanged lips, to prevent the lips from actively
compressing the breast and relegate them mostly to creating a seal.
        A shallow latch can destabilize the tongue and cause the infant to use
the lips to create postive pressure on the breast (normally the job of
the tongue).  This is consistent with the dimpling you are seeing, the
mouth is not filled with breast tissue, so there is excess space, which
means the baby must use more negative pressure (suction), which the
cheek musculature is not able to withstand.  Keitha's suggestion of
holding the baby more firmly will help if this is a case of the baby
sliding down onto the nipple after latching.
        It's up to your eye to determine which is the root cause so it can be
dealt with.  This is my favorite part of being an LC, the detective
work!
--
Catherine Watson Genna, IBCLC  NYC  mailto:[log in to unmask]