I have sleep apnea that was not dx until my youngest was about 2 years old.  I
slept with all three children and never had a problem.  With sleep apnea, you
quit breathing several hundred times a night.  Each time you become apneic,
you wake up, usually not totally awake but enough to remember to breathe.
This also means you never really get to deep sleep.  I always knew my baby was
beside me in the bed.  The patient you describe does sound more like
narcolepsy.  I would fall asleep while in conferences or sitting down charting
or even giving shift change report but not if I had anything stimulating going
on.  I would think labor would be pretty stimulating.
Just thought I would add my $.02 worth.
Kellie Richardson RNC, IBCLC
Mother's Touch.