A report has found an obstetric registrar and the Canterbury District Health Board did not provide appropriate care during a complex labour in 2011.
Health and Disability Commissioner Anthony Hill says the registrar assessed the 34-year-old woman following changes to her baby's heart rate.
The registrar then went ahead with an instrumental delivery and the baby required resuscitation and was transferred to intensive care.
Mr Hill says the registrar made a series of poor decisions and did not recognise the complexity of the labour, including that the woman had Type 1 diabetes.
The Canterbury DHB accepts it did not provide an environment to protect those involved.