H.H.
DH = dear husband
ds= dear son
dd = dear daughter
STTN - sleeping through th enight
dc = dear child
LO = little one
btw = by the way
wdyt = what do you think
wwyd = what would you do
These are the ones that I come across often in parenting boards. Understandable that they don't make sense yet, but pretty soon you'll be using them too!