Deep Sleep?

I have been known to be a notoriously light sleeper.  Any little noise, ray of light, or slight movement in bed normally wakes me up.  Since Elsa has arrived my sleep pattern has completely changed.  Steve can get up and out of bed, make noise getting ready for work, etc and I don't hear a thing.  But if Elsa makes even the slightest whimper I am wide awake.  I guess my sleep evolution has adjusted for survival. Survival of my sanity that is.