Denise,
Interesting that this baby clicks while jaw compression is occuring, usually
clicking occurs when the mandible is dropping.
You are exactly right about the source of this click, it is the tongue coming
off the breast forcefully enough to break the negative pressure in the mouth.
 I have also seen babies thrive despite an audible click, and if mom is not
sore and baby is growing, you can certainly leave it be.
        Have you checked for a mild ankyloglossia (tongue tie)?  I almost
always find this in 'clickers'.  Sometimes the click-sucking is compensatory,
it keeps baby from being drowned when mom has a forceful MER, and if baby is
coerced to stop clicking, they show distressed swallowing and gulping.  It is
possible that this is what is happening in your case - the baby is clicking
when the posterior tongue depresses to catch the bolus of milk that is
expressed from the breast on jaw compression.  Often babies with ankyloglossia
are less able to configure (cup) their tongues, which would make a pool for
the milk and allow a controlled swallow.  Without proper configuration, the
milk would slide down the throat in an unorganized fashion.  Perhaps this baby
is making a deeper depression with the tongue to compensate for the inability
to longitudinally configure the tongue.  I hope this is understandable, I
think the baby is making a front - to - back "pool" with his tongue instead of
a side to side container for the milk.  The extra amount he needs to drop his
tongue is too much to maintain the negative pressure in the mouth, and the
clicking sound results from both air rushing in and the tongue rebounding on
the floor of the mouth.  Of course this is speculation, sight unseen, but it
makes sense based on a functional knowlege of suck mechanics and the usual
compensations.  I'd be interested to know if you can find evidence for or
against such an interpretation.
        If this baby has a slight tongue tie, feeding in a more upright
position (like a football hold with baby brought up higher to mom's breast
while mom leans back) may allow baby to feel more in control of his
swallowing.
Please keep us 'posted' on this interesting little guy.
Catherine Watson Genna, IBCLC  NYC  [log in to unmask]