Ms Miles dialled 111 and yelled out asking if those in the car were okay before waving down an approaching car for help.
The driver of the crashed car called out saying she was already on the phone to police.
"She said get my son, get my son -- so that was the number one priority to get him out."
Ms Miles and the man, who had pulled over to help, pulled the young boy out through the smashed back window.
They cleared broken glass and the driver managed to exit the up-turned vehicle with little assistance.
Ms Miles said the only blood "on-site" was her own.
"It was from my leg from kneeling down on glass."
The 18-year-old driver had been travelling east with her son just after 9am to her graduation ceremony at Wairarapa Teen Parent Unit.
Wairarapa police Senior Constable Harvey Pope said the woman had "come over the brow of the hill and she's gone on the other side of the road and then over-corrected".
"She's lost it sideways and gone into the brow of a ditch and somersaulted."
The crash happened on a straight stretch of road with the car landing upside down on a fence and narrowly missing a power pole.
Mr Pope said a distraction may have been a contributing factor to the crash.
"The weather conditions were perfect, it's a straight road so there is no rhyme nor reason."
Constable Allan French said the pair was very, very lucky.
"It could've been a lot worse -- we are lucky we are not looking at a double fatality."
The car had scraped alongside the power pole, on which marks from the white Toyota Corolla remained.
Mr French said thankfully the young child had been secured in a car seat, because "it looks like it flipped a few times".
The mother and son were taken to hospital by ambulance.
They were treated for shock and shoulder injuries that were caused by the seatbelts.
"We have had so many crashes since Friday," Mr Pope said.
"People need to take care."
