Does retiring your Sim make the baby not grow up?

Yes it will

if you have other playable players, you can use them to help the child grow up and finish the activities needed. If you click on the child, under the name and picture should be an icon that will give you option to let child become adult or stay that way until you're ready for them to grow up.

i’m scared

I have that kind of problem too, after my Sims had a baby
I was going to finish the baby event,but accidentally clicked the retired button,i really regret what I did,can you still have events with the baby,even without the parents?

I have this issue too. I’ve done relationship events daily with the adult child instead of the retired parent (accidentally retired and mad tbh) and it’s been about a month and the baby will not age up.

Any Sim can complete the relationship events with the baby. It does not have to be the parents.

this is not true, the baby will still grow up.