16 month old slow to develop - anything to worry about?

[daisyhun]

My friend has a 16 month old DS who has only just started to crawl, can stand but shows no signs of walking. He does not speak (only says mamamama indiscrimnately) and does not point at things when asked or show any signs of understanding. He never points at anything. He's always been incredibly laid back and placid.

I feel at a loss as to how to reassure her because my 12 month old DD is walking, starting to try to say words, and seems to understand absolutely everything I say, pointing to all of her body parts, things in the room, even starting to learn colours.

I have tried saying it's normal and they all develop at different rates and he has been referred to a paedeatrician but in the meantime my friend is very worried - does anyone have any similar experience?

Ds2 is 13 months and not sitting yet! Also VERY laid-back and placid. Ds1 was a late developer too (though not quite so late!) - crawled at 9.5 months and walked at 22 months.

ds is 21 months and not walking yet. he only said mum until he was 17 months and then all of a sudden came out with shoes. 5 months ago he was very behind all the babies of a similar age with talking, now he is actually ahead of most of them. instead of coming out with a new word say every month from i dunno 10 months he decided to come out with 3 or 4 every week from 17 months and has now caught up well and taken over a few.