I have mixed feelings on this one because I would have been happy if my ped had broached this topic with me. I was the one concerned with my ds with 6 months old because he was so easy but also kinda distant. He never cried unless you took him away from me. But, he did not engage as much as his friends. My friends thought I was nuts until he turned 1.5 and more problems started arisng.
So, just pay attention to your gut and what you think. All babies develop at different times but there is so much great early intervention therapy that if you start to feel unsure, at least get an evalutation.

Good luck.
Sue

I understand you feelings as I have been there myself. My son didn't sit on his own until closer to 9 months. I knew in my heart that he was not retarded but I also knew that there was something a bit off. He has been diagnosed with low muscle tone among other things. I don't think you need to worry at this point, however, be diligent and listen to your pediatricians concerns and recommendations. It seems to me that she has your childs best interests at heart.