dear listners
found this in Sweet (Ed) Mayes midwifery, 1997, p388ff
anatomical onset of 2nd stage is full dilatation of the cervix which may or
may not co-incide with the urge to bear down, and this may not occur until
the presenting part descends enough to compress the tissues of the pelvic
floor (I think this is the issue with feedback through the pelvic
splanchnics I think that is the spelling!) Ferguson's reflex is initiated
with stimulation of nueral receptors in the pelvic floor when the pp
descends into the vagina at approx 1cm above the level of the ischeal
spines. This distension of vagina and compression of pelvic floor initiate
the reflex, which explains why it can occur without being 'fully' and not
even with full dialtation. It would be similar positive feedback pathways
to those that sustain micturition and defecation once it is initiated, I
would imagine.
I think, I'm not a physiologist though. But it all makes sense because it
concurs with my observations. Sweet goes on to talk about physiological
and directed pushing. Another discussion, but also very interestign.
Cheers, Trish
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