A gynaecologist faces possible legal action for inserting an intrauterine contraceptive device without the patient's consent.
The unnamed gynaecologist, Dr B, inserted the device at a private hospital in 2015, after the equipment needed for an alternative procedure for heavy menstrual bleeding failed.
He said the Mirena brand device was the safest and most easily reversible option, avoiding the need for another anaesthetic later.
The patient had not given verbal or written consent and demanded its removal immediately after she found out.
The Health and Disability Commissioner, Anthony Hill, has referred the case to the director of proceedings, saying informed consent was at the heart of consumer rights and the patient was deprived of it.
"The doctor knew that this patient had not consented to the insertion of the IUD and proceeded to insert the IUD anyway, and that was not clinically necessary in these circumstances.
"It was entirely possible to wait to discuss treatment options again with the patient after the failed procedure and that did not occur."