Matthew Holden, who worked for the Yorkshire Ambulance Service NHS Trust (YAS) from 2007 to May 2015, fathered a child with the 22-year-old woman who had a history of taking overdoses.
Mr Holden was called to her home after she had consumed alcohol and the drug mephedrone in the early hours of July 4 2014, and took her to hospital as she was at risk of self harming.
A panel of the Health and Care Professions Council’s Conduct and Competence Committee heard that during the journey the pair exchanged numbers and Mr Holden returned to the address hours later for unprotected sex.
The issue only came to light when the service user had to give the name of Mr Holden as her child’s father during care proceedings in early 2015.
HCPC panel chair Debbie Hill said: “Mr Holden has shown insufficient understanding and insight.
“He made a decision that amounted to a serious and deliberate breach of trust, with reckless disregard for the consequences.
“This was a major transgression of professional boundaries with a vulnerable service user.”
Mr Holden, who had said he was “sorry and ashamed” of his conduct, was struck off the HCPC register from June 22, and an interim suspension order was imposed to cover the appeal period.
A YAS spokeswoman said the trust suspended and investigated Mr Holden as soon as the allegations came to light. He was dismissed in May 2015.
She said: “His conduct was found to have fallen well below the standards of professionalism expected.”