"However, in the best interests of [the woman], I was to give her a sense of support and help in a difficult time, therefore I administered normal saline, leading her to believe it was Pethidine.
"I knew it would do no harm, and that pethidine could still be administered at any stage."
The woman wasn't given any real pain relief for about 2.5 hours during labour.
Hill described the midwife's conduct as "disgraceful" and said that by not providing the woman with the medication she had requested and agreed to receive, the midwife ignored the fundamental importance of consent.
"It was the woman's right to make an informed choice about the pain relief she was to receive, and not to be given IV normal saline when she had not consented to this," Hill said.
"The midwife's conduct in misleading her client during labour by administering saline and telling her that it was pethidine was not only dishonest, but also showed a concerning degree of paternalism.
"Such behaviour by a midwife is an abrogation of the essential partnership between the midwife and her client, which lies at the heart of the midwifery model in New Zealand."
Hill recommended that the midwife undergo further training about the Code of Rights, informed consent, and communication with clients.
He also recommended that the Midwifery Council of New Zealand consider whether she should undertake a competency review, and she provide a written apology to the woman.
The midwife told the HDC that she had been registered as a midwife for 23 years, and that she was deeply regretful of this situation.