I think you are supposed to go by the adjusted age but my son, born at 39 weeks, didn't start smiling until at least 3 months if I remember right so i wouldn't worry yet.

Try not to compare your kids. I know it's hard, because I am on my 4th and have looked at the 1st year calendar of each of the older boys! BUT each child is different. If you have a concern because of developmental milestones talk to your pediatrician, but trust them. Even your twins are going to develop on their own unique schedule. I suggest you just relax & spend more face time with the babies....... they love to see us smiling and talking to them! I'm sure you will get those precious smiles soon!

My daughter was born at 31 weeks and is now almost 5 months old. The best advise I can give you is don't go by the weekly/monthly milestones! Even full term babies don't always hit the milestones at the time specified. Your doctor will tell you if there is cause for concern. My rule of thumb was if she wasn't showing development or progressing to the milestones by the corresponding gestational age, I would talk to the doctor about it.

Since you have twins, I guess you can also compare their development as time goes on.

As for the smiling, my daughter didn't start socially smiling (not gas smiles) till after her 2 month check-up... I think like week 15 or 16.

Hope this puts you a little bit at ease!

I go by my girls' adjusted age. They were born at 33 weeks and are almost 9 weeks old. (Adjusted age of 2 weeks.) Although they smile occasionally, they are not smiling as a reaction to what's going on. I'm looking forward to the first time I see that "real" smile.