A driver distracted by her ringing cellphone smashed into a tractor-trailer in Brooklyn early yesterday — injuring her two adult passengers but remarkably leaving her baby boy unscathed, witnesses said.

“I looked away, and the car went out of control,” said Carmen Natel, 31, who’d been driving two female co-workers home from a party at their boss’ house.

Security guard Hendrick Aguy, 28, pulled 10-month-old Jaydi from the mangled wreck on Humboldt Street and Greenpoint Avenue at about 1 a.m.

All four people in the car were taken to Bellevue Hospital.