One example can be *Glue ear*
Glue ear can impact on a child's speech and language development and also their hearing.
Say there is a 3 year old girl, and this 3 year old has glue ear, she may have speech delays and may only say a few words that are clear, compared to a child without glue ear who should be using a lot more words and communicating easily.
The little girl with glue ear may have problems hearing and this is the reason why the speech is delayed.
Here is some information on glue ear
http://www.nhs.uk/conditions/Glue-ea...roduction.aspx
Glue ear is just one example there are many more additional needs that impact on development such as:
cleft palate
English not being their first language
disability
Autism
and many more.