I would assume total medical bills between $10-15k for a healthy pregnancy and hospital birth with no significant complications. That gives you a starting point for calculating coinsurance costs. If your baby is born quite early or needs surgery, then your costs will be much, much higher and you'll almost certainly hit your out of pocket max. 10-15% of babies born in the US spend some amount of time in the NICU, so it's not very unlikely you'll have high costs due to a NICU stay or other complications.

If I assume your total healthcare costs are about $12k before insurance, then your total cost with the HSA plan is $6,680 for the year. If you go with the PPO plan, then it's $8,404 for the year.

If you have meaningfully higher costs due to complications, the HSA is the better pick because the out of pocket max is lower and the premiums are substantially lower.

I'd pick the HSA plan, and max out your HSA so you are spending tax-free dollars to pay your medical bills.