I was in the same position you are in - waiting for both a baby arrive and training to begin. I chose to have the baby first, then begin training 6 weeks later.

If I would've done training first then the baby delivery it would've been a disaster. I think you'll put your 121 career and family at risk, in exchange for a few months' seniority.

An airline training schedule is a best case scenario only, delays are almost assured. You may have to wait for sims, extra sim sessions, insteuctor or check airman calls in sick, wait for IOE or more IOE time needed.

Planning to complete training and IOE exaxtly as scheduled leaves no room for realistic setbacks. Training is never completed early, it is easily and often delayed.

Also, our baby arrived 2 weeks early. Will yours be early, potentially during IOE or sims?

Do you want to go to systems, sims and your checkride while your wife goes through the 3rd trimester alone?

A friend of mine in his first year at a regional was given 2 weeks unpaid leave for childbirth. I wouldn't expect 6 or 12 months to be granted, even if it was given you would have currency issues.

There's an awkward conversation coming between you and the airline. Tell them now and make plans to assure support for your wife and son. Take as much unpaid (unemployed) time as you want. Push back the training date then your fam can support you in training.