Wife enrolled in second medical plan after giving birth…

My wife gave birth several weeks ago. When we arrived at the hospital, I provided our Aetna POS II medical plan (through my employer) information through which she was (still is) covered. The day after our child was born, I informed my employer and the child was added as a dependent to the Aetna plan.

I just learned that my wife enrolled herself and our newborn son in a United Healthcare medical plan provided through her employer several weeks after our child was born (within the 30 days). This was not done maliciously. She received bad advice.

The United Healthcare plan became the retroactive primary for my wife and child (birthday rule) with coverage beginning the day of birth. I only found out about it recently, when Aetna discovered it while processing a $100k+ NICU claim. I have since provided each carrier with the other’s info to coordinate benefits.

Chronologically, the Aetna plan was the only medical coverage that my wife and child had while in the hospital for the birth event and subsequent NICU services.

I am wondering…

What is our financial exposure for procedures that required prior-authorization from Aetna? Is United Healthcare obligated to assume financial obligation for Aetna’s authorizations?

Will Aetna reverse all claims that they have already paid out if they retroactively became the secondary payor upon activation of the United Healthcare plan? Should we insist that they reverse the claims so that we can have the providers submit to United Healthcare?

Is there any way to have the United Healthcare plan rescinded?

Thanks for any guidance.