8.5 month old not sitting well or attempting to crawl/commando crawl/drag. Problem?

[SleepyCaz]

My DD is 8.5 months and has not yet mastered sitting. She can sit for maybe 30 seconds, but as soon as she tries to reach for anything, she topples over. Or if she looks up, she falls backwards. She can roll from back to front, but not the other wat around, and she has no interest in trying to crawl.
My DS, now 3.5 was super active from about 5 months. Am I worrying over nothing or should she be able to do all of this, or at least the sitting, by now?
She is in the 100th percentile for both lenght and weight, and theHV's have said this is fine as they are balancing out, ie, if she were in the 50th for length, but the 100th for weight, she would be too fat, but they say she is just a big baby.

My 3 youngest dds were all huge & tall babies they were all late sitting well and moving.

One of them couldn't sit unsupported until she was 11 months. 2 of them didn't crawl until they were nearly a year old........

8.5 months isn't very late for unsupported sitting but keep an eye on it and see whether it improves by 10 months or just go take her to the HV if you really are unconcerned.

Some babies are fairly placid and happy to sit and watch the world go by......enjoy it whilst it lasts!

My 11 month old (who is tiny) was only sitting well at about 9 months and still isn't showing any interest in crawling. He's my third and is identical in weight and physique to my first. She crawled at 6 months and walked at 11 months. Go figure ... But I'd say it's certainly nothing to worry about yet. As CarGirl says, keep an eye on it and try not to worry (she said, knowing that we mother's CANNOT not worry!).

My baby turns 10 months this Thursday and still struggles to sit on her own.I'll hear what the docter says on Friday. I am getting worried,Ihope she picks up soon.

a mommy