There are tow ways:
one: When you try for baby when you finish you will hear a sound.
two: When you are in neighberhood press: ctrl+Left shif+ c and type boolprop testingcheatsenabled true. Now when you finish try for baby shift-click on your sim and
click spawn and then click tompstone of l and d. Now left-click on the tompstone and try
find speed up my pegnasy.
Note: If you don't know how to try for baby, build a high reletionship with a sim and relax to a double-bed the click on the other sim and select cuddle and the try for baby.
I hope my advice was enough helpfull.

The sound is a lullaby