The Health and Disability Commissioner has found that a hospital midwife and a doctor were at fault over the death of a baby soon after birth.
Anthony Hill released his decision on the case on Monday.
The inquiry followed a complaint from the baby's father, but provides no names of any of those involved in the 2008 case, or where it occurred.
The unborn baby was large and the mother was asked to give birth in hospital rather than at home as a precaution.
Labour was difficult, and the hospital midwife became increasingly concerned - but rather than calling in more help, she deferred to the obstetric registrar.
Mr Hill says the registrar misread a CTG trace, which monitors the baby's heart rate, and failed to seek more senior help. The baby needed resuscitation after delivery, but died soon afterwards.
"The most significant error was that, a trace that was monitoring the child's heartbeat during the birthing process was not accurately interpreted, was not read properly over time, and key warning signals - of which the trace was only one - and in the event, not acted on."
Anthony Hill says the obstetric registrar should have realised that there was a problem, but didn't, and the hospital midwife, who did realise there was a problem, should have alerted the on-call senior consultant.
Mr Hill says the DHB was not to blame, but must encourage better communication between staff in future.
The commissioner warned all health professionals to seek extra help if they have concerns about a patient that are not being heeded.
"If a professional as part of a multi-disciplinary team has concerns, always ask the question and always hunt down the answer.
"And if there is disagreement, then get a third party or a third voice into that conversation."