"It gets extremely hot down in the pram, something like a thermos", he said, speaking to the Swedish Svenska Dagbladet newspaper.
"There is also bad circulation of the air and it is hard to see the baby with a cover over the pram."
He explained that if a child were to get too hot, they may think they are back in the womb again and "breathing may stop".
A Swedish study carried out by the paper found a covered pram that was left in the sun became 15 degrees hotter than a pram left uncovered.
Sudden infant death syndrome can also be caused by overheating, and avoiding thermal stress has been one of the strategies used to reduce the risk of SIDS.
It was recommended parents leave their sleeping baby's face uncovered to protect them from overheating.