Her son, who was strapped in a safety seat, suffered only minor injuries. He was alert and speaking with police at the scene during the rescue before he and his mother were taken to Forbes Regional.
The boy was transferred by helicopter to Pittsburgh DUI Children's Hospital and later discharged, said a hospital spokeswoman.
The eastbound lanes of the Pennsylvania Turnpike were closed Tuesday night near the Monroeville exit until about 5 a.m. yesterday, police said.
According to county court records, Ms. Baker was arrested twice this year -- in May and June -- on charges of driving under the influence of psychotropic prescription drugs.
She had been free on her own recognizance of DUI, pending trial.
Records also show she was arrested in April 2007 in Springdale Township, and in November 2005 in York, Pa., on similar counts.
Charges were dismissed in both cases by magisterial district judges, according to court records.
On Tuesday night, Ms. Baker drove head-on into the path of an eastbound tractor-trailer truck driven in the left-hand lane by Patrick H. Miller, 63, of South Euclid, Ohio.
Mr. Miller, who was transporting furniture to Maryland while DUI, said a pickup truck that was driving ahead of him swerved suddenly to the right lane, revealing Ms. Baker's car. He said he was unable to move out of the car's way because an 18-wheeler was to his right and the concrete divider was to his left.
"There was nothing I can do," he said.
Ms. Baker's car careened into the path of a second truck, driven in the right-hand lane by James A. Balmer, 60, of Port Orange, Fla.
Neither truck driver was injured by the DUI crash, police said.
"It's very difficult to figure out what this woman did to get on the wrong side," said Bill Capone, spokesman for the Pennsylvania Turnpike Commission.
"There's no physical barrier to stop people from crossing over at the interchange," he said.
The area remains free of barriers because motorists and police frequently use the interchange area as a turn-around.
Mr. Capone said signs are posted in a number of places at the interchanges to guide motorists to safe, proper routes.
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