The woman, who is in her 30s, and her infant were found seriously injured by a passerby at the Dalby quarry outside Lund late on Tuesday night. Both were rushed to hospital but succumbed to their injuries.
After initially suspecting that it was a tragic accident, the police are now treating the deaths as a suspected double murder. Police suspect they may have plunged to their deaths from a drop as steep as 15 metres and have arrested a local man.
Regional newspaper Sydsvenskan reported that he and the woman had been in a relationship and that they were the parents of the dead baby.
"There are two people that have died and we have arrested a suspect, a man," Stephan Söderholm, information officer of the Skåne police told the newspaper.
The crime scene was initially cordoned off by investigators while the woman's house was also examined. An officer working on the case said police were trying to find out why the woman and her baby were at the quarry in the first place.
"Dalby quarry is not the kind of place you would normally spend a Tuesday night in December. It's a dangerous place with steep slopes," added Söderholm.
The quarry is described in tourist literature as a "beautiful, tranquil spot" and is a popular location for visitors to southern Sweden during the summer.
On Wednesday afternoon the police cordon was lifted and officers said they were appealing for any witnesses to come forward.