Hi Elisheva,
Sucking is a complex interplay between compression (positive pressure)
and suction (negative pressure).  In order to generate positive
pressure, the baby must have something to press the breast against with
the tongue.  If there is a unilateral cleft, the baby may be able to use
the tongue asymmetrically and press the breast against the intact half
of the palate.  If there is a bilateral or midline cleft, there may not
be enough palate for the baby to press the breast against to generate
compression.  After all, the tongue can only lift so far to press
against the breast...this is part of the problem with tongue tie, the
tongue cannot lift enough to press milk from the enlarged ducts under
the areola toward the nipple.

After milk is pressed toward the nipple, the soft palate closes off the
pharynx and the rear half of the tongue drops to enlarge the oral
cavity, producing negative pressure (suction) that encourages the milk
to spray out of the nipple onto the depression on the tongue.  The
longitudinal groove in the tongue allows this milk to be gathered into a
little bolus, which is then swallowed.  Then the soft palate relaxes and
the infant breathes.  There is some controversy over exactly when the
swallow happens in terms of the respiratory cycle, but most think it is
in the end-inspiratory pause.  The little sound we hear when a baby
swallows properly is actually the interruption of the breathing as all
this happens.  If there are any OT's or ST's on the list, they can give
a clearer and perhaps more current picture.  Anyway, if the soft palate
is cleft, it cannot close off the oropharynx, so no negative pressure is
generated.  It also cannot seal off the airway, so milk can go up the
baby's nasopharynx and out the nose, into the ear, and down the
trachea.  Though human milk is isotonic to tissue fluids, it still is
not very comfortable to have it in places it does not belong.  And milk
that leaks into the airway effectively narrows the airway, increasing
the work of breathing.

I hope this answers your questions.
--
Catherine Watson Genna, IBCLC  New York City  mailto:[log in to unmask]

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