Police said the baby was born in a hospital last Monday and was dumped in the drain on Tuesday.
The crying baby was heard Sunday morning by passing cyclists, who had to lift a heavy concrete slab to find him 2.5 metres down at the bottom of the drain.
The mother was arrested by police Sunday and was arraigned in court Monday.
Police allege she forced the baby through a crack in the drain's concrete cover where he lay undiscovered for five days. He is recovering in hospital.