QLE and out of pocket max

We are family planning and looking ahead to insurance for next year. I know having a baby and adding them to the plan will be a qualifying life event and we have 30 days from their birth to get them covered and it will be back-dated. My question is related to the deductibles and out of pocket maxes in the transition. Is a single person deductible (what I had prior to giving birth) or a family deductible used (what I’ll have when adding my child) for delivery?

For example: my current deductible is $2500 with a 5k out of pocket max. My family deductible is $5000 with a 11k out of pocket max. If I give birth and it’s just me on the plan, but then say 2 weeks later I add our child to my insurance will my delivery charges me applied with a $2500 deductible in mind or with a $5000 deductible in mind? I know they’re billing based on the DOS, so on the DOS I had a $2500 deductible but I’m then going to add someone (with backdated coverage) increasing my deductible. I’m just trying to get a ballpark for what my actual delivery deductible would be as the cost difference between $2500 and 5k is a lot. Does that make sense?

I’m also wondering that if I choose to change my insurance tier when I add my child how that could change the deductible and the bills from birth. Since it’s a QLE I can not only add someone but change the plan I’m on. I am currently on a $2500 a month deductible plan but my employer offers a $1500 deductible plan for a much higher premium, if I give birth early on in our insurance year should I get on the lower deductible higher plan to start so the birth is cheaper and then go to a cheaper plan or will it not work that way?