When your child is Born, you hope and pray the child will be perfect. All the parts work, reposes are good, in the USA, this was called an Apgar of 10. I can remember when my first child was born, and they said "he is fine, but has some physical problems", which began us on the long road to what was club foot and how to deal with it and all the therapies and surgeries it entailed. That child is a physically normal adult today and a dad himself, but at the time, what nightmares we had.
Developmental delay is when somewhere in utero, the development of the baby did not go as programmed. there could be issues with muscles, as club foot or CP, or oral motor tone, that leads to feeding issues, and syndromes, such as fragile x, which have physical and mental delay, the amounts od delay, what kind of delay, are never quite certain at birth. But what is certain is that you, as the parent, will have to add into your life the people and professionals that will help you along the way. All these delays can affect speech, with poor tone, affecting speaking, or muscle problems affecting the ability to produce sounds and words, and the cognition, of forming thoughts and language.