The pair exchanged a large number of texts while the midwife was caring for the client, some of which were of a sexual nature.
The pregnant woman became suspicious but when she confronted her husband about it he twice denied there was any impropriety in his association with the midwife.
The summary of facts recorded that the pregnant woman felt "as if she was going crazy thinking that her midwife was sleeping with the father of [her] children".
The woman explained that the discovery of the affair had a devastating emotional impact on her and her family. She said she felt distressed about the need for her and her infant to undergo testing for sexually transmitted diseases.
The midwife expressed regret and attempted to apologise to her client, including writing a letter.
The New Zealand Health Practitioners Disciplinary Tribunal found the midwife guilty of misconduct and malpractice.
The director of proceedings accepted the midwife's name should not be removed from the register because of her remorse and rehabilitation efforts.
The director also noted that usually a suspension of nine to 12 months would be warranted but was not necessary because the midwife had removed herself from practice for five months. She also had counselling, had been transparent about the complaint in seeking a new job, undergone a midwifery standards review and had mentoring.
She was censured, ordered to pay costs and ordered to continue with her mentoring and counselling for a period. She was also prohibited from providing care to friends or family for 18 months and had a limit placed on the number of clients she could see for 24 months.