The accident occurred under the Molete flyover, as the woman and two men were caught in the middle of the road by the speeding truck while attempting to cross over to the other side of the road.
Eyewitnesses said the deceased and the men were trying to beat the oncoming truck by running across the road to the other side, but the pregnant woman fell in the process and was crushed to death.
The two men, however, managed to escape unhurt.
The corpse of the victim was evacuated and deposited in the morgue of the Oyo State Specialist Hospital, Adeoyo, by officials of the Federal Road Safety Corps.
The spokesman for the FRSC in Oyo State, Mr Seun Onijala, confirmed the accident, adding that officials of the agency quickly moved to the area and cleared the obstruction to traffic, and deposited the corpse in the morgue.
Onijala, who is the Deputy Route Commander, said the articulated DAF 85 truck had no number plate.
The driver was said to have been arrested and detained by the police.