Hospital Billed Wrong Insurance Now Telling Us We Owe $$$

Location: Delaware

I gave birth to my baby in September 2024. I filled out the pre admission paperwork requested by my hospital with the insurance info for the policy the baby would be on. My husband and I are on separate plans and baby was going on my husband’s. All paper work was properly filled out and handed in upon check in at the hospital.

This fall (October 2025) we start getting calls from the hospital telling us that the insurance info is wrong and we need to update them. Turns out the hospital billed MY insurance for my newborn. My insurance originally paid the claims but took them back a year later. We didn’t know any of this happened until the call from the hospital a year later. I provided the correct insurance info to the hospital and they resubmitted the claim. We just checked the insurance portal and can see that the correct insurance denied the claim due to it being “outside of policy time limits” or something like that. We have not heard back from the hospital yet but are preparing for the worst.

I would like to know if we have a leg to stand on here to fight against this $11k bill potentially coming our way. What are our rights and how do we go about fighting this? Any advice is greatly appreciated.

ETA: Baby was added to dad’s insurance policy through standard “life event change” process within the correct timeframe required. All of baby’s claims post hospital stay for delivery were covered and approved on said insurance plan.