The patient had declined the device in the past and had not given consent to have it inserted on this occasion, but Dr B went ahead with the insertion, considering it to be the safest and most easily reversible treatment option, the report said.
While in the recovery room, the patient discovered what had happened and was distressed, so Dr B apologised and removed the device.
"It is plainly unacceptable that Dr B inserted the Mirena without have first obtained Ms A's consent," the report said.
"Ms A was particularly vulnerable as she was under a general anaesthetic."
In the investigation into the incident, the patient told the commission she was clear in telling Dr B she did not want the device fitted in previous meetings, but Dr B continued to suggest the option and persuaded her to include it on her medical insurance forms in case she changed her mind.
When inserting the device, Dr B considered it could be an interim measure until further options could be discussed with her.
"He also noted that Ms A had advised of her anxiety about general anaesthetic, and wanted to avoid her having to be placed under an anaesthetic for a third time."
The patient told the commission she felt "very angry about this abuse of my wishes".
"I actively, firmly, and clearly stated numerous times that I did not want a Mirena," she said.
"At no point did my position alter. He wanted me to have it. I felt pressured but I am [a] strong person and felt able to say no.
"I firmly believe he was aware I did not want a Mirena and that he used the circumstances to do what he felt I needed, not what I wanted. He acted against my express wishes."
Dr B told the commission the patient had expressly declined the Mirena during a previous procedure but had not expressly declined the option on this occasion, and had used it between each of her pregnancies without any issues.
The patient said she never told Dr B she'd had it fitted previously, and said she'd only had an IUD inserted between one of her pregnancies, though she was not sure if it was the Mirena brand.
Dr B later said he accepted he did not make the right decision, and it was an error in judgement that he did not intend on making again.
"I am highly critical of Dr B's actions," the commissioner said in the report.
The commissioner referred Dr B to the director of proceedings to determine whether any proceedings should be taken, and recommended Dr B undertake further education and training on informed consent.
The commissioner recommended the private hospital use the case to educate its staff, and provide the commission with an update of the corrective actions it has taken since the incident, including copies of the updated consent form and informed consent policy.
The commissioner also recommended that the Medical Council of New Zealand consider whether a review of Dr B's competence is warranted.
