A Kansas doctor is accused of breaking the law in his handling of an abortion on a 13-year-old girl, but he says he did not realise her age.
A state board is weighing disciplinary action against Dr Allen Palmer over the procedure he carried out in 2014 at the women's group Planned Parenthood.
State law requires that foetal tissue from abortions on patients younger than 14 be preserved.
Dr Palmer said he relied on staff to tell him the age of patients.
Under state law in Kansas, abortions can be provided to children with parental consent.
The part-time Planned Parenthood contractor told medical regulators on Thursday he typically did not perform abortions on patients so young.
The Missouri resident has been licensed to practise osteopathic medicine and surgery in Kansas since 2008, according to a petition against him by the Kansas State Board of Healing Arts.
He was filling in for a doctor on holiday when he performed an in-clinic abortion on the 13-year-old girl.
She had been impregnated by her 19-year-old boyfriend. The foetus was nearly 11 weeks old.
The organisation self-reported the violation to the state.
"I'm as shocked and awed by this failure as anybody here, but they want to hang it on me, and maybe that's the way it is," Dr Palmer told the state board, which deferred its ruling after the hearing.
"I'm telling you that I did not know and I would not have proceeded if I had known."
The petition against Dr Palmer was filed by the board's deputy litigation counsel, Susan Gering, and alleged that he failed to preserve the tissue and submit it to the Kansas Bureau of Investigation.
It called for revoking, suspending and censuring Dr Palmer's licence, or placing him on probation for the incident.
When asked by a board member whether he thought to ask the patient's age, Dr Palmer said: "I really don't ask them, because teenagers today, the way they dress, I can't tell how old anybody is."
He added that patients typically go through counselling and screening before meeting him.
"I'm the last person in line for them. If there's a problem, the staff raised it to me or they notified me somehow," he added.
His lawyer argues Dr Palmer had not received proper training on Planned Parenthood policies and procedures regarding operations on minors.
Meanwhile, the women's group has argued that Dr Palmer "found it unnecessary to familiarise himself in detail with [state] laws requiring the preservation of foetal tissue extracted during an abortion procedure" on a minor.