The son of a Florida fertility doctor faces up to 13 years in prison after tricking his pregnant girlfriend into taking an abortion pill, causing her to lose their baby.

John Andrew Welden, 29, pleaded guilty to "tampering with a consumer product" and "conspiracy to commit fraud" in Tampa court. He accepted a plea bargain which meant he avoided being charged under the federal Unborn Victims of Violence Act, a murder charge carrying a life sentence.

Welden's lawyer told reporters of the bargain: "The possibility of a mandatory life sentence, no discretion to the judge, obviously is a big factor.

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"Obviously it's tragic all around from every angle, and I think that's recognised."

Welden was reluctant to be a father when his then girlfriend, Remee Lee, told him she was pregnant. After a sonogram at his father's clinic, Welden told Ms Lee her blood tests had shown that she had an infection and needed to take amoxicillin.

He gave her pills, which he said were the antibiotic amoxicillin. But they were actually Cytotec, a drug that causes contractions, which he got his hands on by forging his father's signature. He told her to take three of them a day.

After she took the first, Lee was rushed to the hospital with abdominal pain and bleeding, and lost the baby.

In May, she told CNN: "Medical professionals saw that it wasn't quite right. Everybody knew it wasn't amoxicillin.

"I can't believe someone did something so malicious to me, and not only to me but to himself. That was our baby."

Ms Lee was sobbing in court as Welden admitted his guilt.

Her lawyer, Gil Sanchez, said: "Nothing is going to bring back what was taken from her."

Welden said nothing as he left the courtroom on Monday. He is scheduled to be sentenced 5 December.