The adult should stay with the baby for 24 hours then leave at 12:00 AM. If you pause your Tama after it goes to sleep then it wont leave so that could be your problem.
At mid-night of the second day* the parent will wake up and turn on the lights, but the baby will remain sleeping in bed. The parent will just stand there for about 3 minutes, then jump up and disappear off the screen. (The lights will turn off again, automatically.) When the baby wakes up in the morning, s/he will be alone.
(* example: if your Tamagotchi character mated and had a baby at 10:30 AM Thursday, then the parent will leave the baby at midnight as Friday becomes Saturday.)
Note: if you pause your Tamagotchi over-night, or adjust the clock to skip past midnight, the adult will not leave. Also, if you pause your Tamagotchi for long periods of time, it may take longer for the adult to leave.
oh yea.. i tend to switch the clock because i stay up pretty late sometimes and i still want my tama to be awake when i am and then i turn it back to normal.
So are they stuck together for the whole time? or will it eventually leave