Sometimes, when kids learn new things, they don't do what they know. Like saying mama, he may be consentrating on his waving and bye. I'd watch and see, but as long as he keeps going forward-I don't think it's a regression. Maybe try to leave the room and see if he calls for you.
With him only being 8 months old, it seems to me that his language might come and go a little. I honestly don't really remember any of my kids saying actual words at 8 months old...just the babbling that would sometimes come out mama, dada, or baba.
It is something to keep an eye on, and if it is something that is truly bothering you I would call your ped or maybe one of your 6 yr olds dr's and explain to them your worries. Explain to them that you are on high alert, but you just want to make sure you can start the earliest possible intervention, if something is there.
Ear infections are also something to watch out for. If he isn't hearing you clearly that would do it to. Sometimes kids won't even show any symptoms like fever, or crankiness, if it's just fluid building up in the ear and not an actual infection.
Hugs!
You'll always worry, of course, but I can tell you that it's common for kids of that age to temporarily lose skills (words, especially) as the focus their efforts on some other skill. This is a well known phenomena, I believe.
Babbling chains of sounds like ba-ba-ba and ma-ma-ma is normal for this age, but it's not really using words. When an older child stops saying the word mama, he loses something functional and meaningful, so it's a clear regression.
For babbling, my instinct is that the focus would be more on the amount or nature of the babbling rather than specific sounds. If there's a dramatic change in the amount of babbling or another dramatic change that happened at the same time, I would be concerned.
If I were you, I'd talk to the pediatrician (and/or EI) and say you need extra support and guidance in monitoring your baby's development, given his older sibling's diagnosis, for safety sake.
Good luck with everything.
I know I am on hyper alert about the baby (8 months).
He has things I worry about (the worst sleeper ever, high-strung, having a hard time with solids) but overall he seems to be developing well (seemingly better than DS, now six with Autism) and has a very sweet nature.
He was saying ma-ma. I wasn't sure if he knew it was me but he was saying it, many times a day for a few weeks. (I know the CDC considers a regression at any time a red flag, but would this be considered one.)
He hasn't said it for four or five days. He is discovering new things during this time, clapping, waving bye bye (again, I don't know that he knows why he is doing these but he is imitating). When I say ma=ma to me, he just smiles and dosen't repeat. He is vocalizing a lot (but just babbling).
Would this be considered a regression? Or, is he just focusing on other things? Should I be worried?
I don't know how to find the balance between being alert to the possibility of Autism and being too hyper-alert.
Raquel