Global Developmental Delay - under 1

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Hi all, I'm in a nc and trying not to out myself so apologies if this is vague or turns into a drip feed - really not trying to be unhelpful but desperately need advice.

I am 'involved' with a family who have three children. I'm not just being nosey about them; I really am very very close to the situation. The older two have some forms of development delay but it's not diagnosed. One parent also has LD. The youngest child is under 1. S/he is meeting milestones currently (pulling up, crawling, making noises etc) and seems to be developing differently to the other two. Delay was already apparent in the other two way before this point.

So my question is around the likelihood of him/her developing GDD. Is there somewhere where I could find that kind of statistical information? And then I have another question about the extent of GDD if it is not evident (at all - that's a paediatric opinion) by the age of 1. How severe could GDD developing after this stage be? Should I be looking to the siblings or is there any statistical/other information on that? Anyone who could point me in the direction of that kind of information also gets my undying gratitude.

TIA

I think you would struggle to find statistical information about this, but plenty of info on GDD.

Imo I think the fact that the baby is doing everything physically on time would rule out a global element unless there is a genetic condition which means this will happen. Probably information you would not have? Then it is clear cut, as in Retts syndrome.

As to the intellectual development that would take longer to show itself, probably starting with speech development, and there is also regressive autism to consider as a possibility.

The sibling's condition may have no relevance.

As you can see trying to predict the future for this child is nigh on impossible. Statistics probably would be no more use to you than guesswork.

Yes I see that. A genetic test might be possible.

But would the regressive autism or other delays be anthing to do with the sibs conditions? I'm trying to establish what the genetic inheritance is here iyswim? I understand that a child might develop all sorts of things but what is likely for this child developing according to milestones at the moment but with something in the family causing siblings' issues (it is likely to be genetic as they don't live with birth parents).

I am hoping that somewhere there is a big calculator which goes:
background risk of any child developing delay = 3% x parent with delay x sibling 1 with delay x sibling 2 with delay / no delay detected at 10 months.

I know there isn't one but some idea of probablity would be useful as at the moment it seems like it could be 10% it could be 90% and no-one will give us any kind of idea of the likelihood of issues further down the line. For example annecdotally do issues tend to show up past a year or are they usually obvious by that time?

Delay is used when development is 'normal' in sequence but typical milestones are not met/met late.

Retts, as an example, is categorically not 'delay' because the hallmark of the condition is a typical development of skills, followed by rapid regression, then a gradual further loss of skills with characteristic features (e.g. hand wringing), followed by plateaus and further small regressions.

Autism is a disorder and can be either manifested by the absence of key skills +/- splinter skills, or fairly typical skill development followed by a sudden regression in some skills.

GDD isn't a condition. It's a description of the extent of delay. The causes of GDD are as varied as hairstyles. That's why there is a massive study happening, mapping the genomes of people with developmental delay.

If the children concerned were delayed in the millstones the 1yo has met, it tells you that either the 1yo doesn't have that delay, or any potential delay is milder, or whatever causes the delay affects different people differently.

The paed said GDD. Which would then rule out something like what you're describing in terms of Retts? (I mean rule out as a cause for what the others present with, not 'rule out' per se)

Rett syndrome is de novo (isolated, not passed down by genetic inheritance) in 95% of cases, so it would be very unlikely to have siblings with Rett syndrome.

Basically, until all milestones are reached, a child can experience delay in any area of development. To have GDD a child must miss milestones in two or more areas of development (motor skills, speech/language, cognitive skills, social skills).

If you are looking at whether the 1 year old is affected as the other siblings are I would agree with what lougle says, as in if they were delayed at 1 year old and not doing the things this baby is doing then it unlikely to be a similar condition. There are lots of genetic conditions but I believe the majority are noticed from birth, so the baby may be unaffected. It could be that it has not inherited the learning difficulty from one parent but the normal genes from the other. There are I think millions(?) of genetic conditions, probably the majority not diagnosable.

The only mathematical thing I can think of is with dominant and recessive genes. If the mother/father has a genetic disability (diagnosed or otherwise) and the genetic fault is dominant then each child has a 50% chance of being affected. If recessive I think it's 1 in 4. (Sorry my biology is very rusty)

So if one parent has some type of genetic defect and it's been passed on to 2 of their children then this 1 year old may be completely unaffected. That's the only statistical thing I can think of.

Right now I am really interested in this statement and would like to know if it's true:

There are lots of genetic conditions but I believe the majority are noticed from birth

Is there anywhere I could check that?

I really really appreciate this advice guys. I know I'm not giving much away but trust me it's really very important to me and you are great for helping me

There are lots of genetic conditions but I believe the majority are noticed from birth

I am not sure this is the case. DD for example has severe ASD, learning difficulties, only little speech and language. We entered 'the system' only at 3 and her difficulties did not really become obvious until 2.

From reading on here and when thinking about other parents of children with SN I know, mostly the DC's SN became only obvious after the age of 1.5 or 2 but rarely at birth.

"There are lots of genetic conditions but I believe the majority are noticed from birth."

I don't want to be unreassuring, but I don't think that's true.

DD1 is a case in point. To be fair, a midwife thought she looked like she had DS because she had a flattened bridge of her nose, but that was dismissed by the doctor. She wasn't then flagged until she was 2 years 9 months. She has 'something genetic', the geneticist is sure, but finding out what the 'something' is is like looking for a needle in a haystack.

She has global issues and goes to special school, but her delays were apparent only to me (my concerns were ignored as I was a first time parent) until she went to preschool.

In the special school my DD goes to, there are a huge number of children with no diagnosis.

The only way you could be sure that a child will not have GDD is if they reach an age where skills in each area stabilise without issue. So, for example, you can't say a child won't develop a S&L delay until they reach the age of 4, say, when a typical child will have speech and language that can be understood by anyone 90% of the time. Until then, they may drift from the 'normal' curve.

For gross motor skills, presumably they can't be deemed not at risk of any possible delay until they can walk, run, hop and jump as other children do. DD1 can jump now at 8, a bit haphazardly, but couldn't at 6. Most children can jump at 3 or 4.

Social skills...well it's usual to 'play alongside' until a child is around 3/4, so they wouldn't be considered delayed until they reach an age where most children play co-operatively, etc.,

Of course, that's quite simplistic, because children don't develop in a linear fashion and it may be quite obvious that something isn't quite right before they reach those ages.

The real difference is that 'disorder' means 'development out of sequence with the typical pattern of development', so that may mean developing 'normally' in some areas of a skill, but not developing other areas at all, whereas 'delay' means 'development that follows the typical development of children in that area but is attained slower/not at all'.