Staff began cardiotocography (CTG) monitoring of the baby's heart, but this was stopped for three hours, while the woman continued to labour in a birthing pool.
When it resumed, the baby's heart rate was above normal, and a caesarean was discussed, but the heart rate appeared to improve and it was agreed to give the woman more time to push.
An emergency c-section was eventually performed, but the baby suffered severe brain damage due to oxygen deprivation and died at six days.
Wall found the obstetrician in breach of the code, criticising her for not adopting a more cautious approach and proceeding with a c-section when she first reviewed the woman.
In the second case, a woman who was induced experienced excessively frequent contractions, and although it was a high-risk birth, fetal heart rate monitoring wasn't carried out continuously and an abnormality wasn't picked up.
The baby was born with a brain injury.
This woman's pregnancy had been monitored by a self-employed obstetrician and gynaecologist. He had done ultrasound scans in his office to monitor the fetal growth, but he did not record the outcomes in the clinical notes and did not detect a growth abnormality in the fetus.
She found him in breach of the medical code and recommended the Medical Council of New Zealand consider doing a further competence review, and that he provide an apology to the woman and undertake further training.
Wall found that a number of failings by the DHB and its staff represented a "pattern of poor care".
"The DHB must ensure that it has in place appropriate staffing levels, policies that provide sufficient guidance, and equipment in good working order, so that staff are supported adequately to provide safe care," Wall said.
Ms Wall was critical of systemic failures at the DHB, including a lack of clarity in policies and procedures.
"These failures left staff without clear instructions and support, and resulted in a failure to monitor the woman and her baby adequately during the induction process, and to recognise the significance of the ongoing tachysystole, or, where it was recognised, to escalate the abnormal CTG by requiring the obstetrician's earlier attendance," Rose Wall said.
Following these incidents, the DHB conducted an external review of its maternity services in 2018, and found several areas of risk that threatened the safety of the service, including staff shortages.
In a statement, Hutt Valley DHB chief medical officer Dr Sisira Jayathissa said she accepted Wall's findings.
"We would like to apologise again to these patients and their families, and again convey our sincerest regret that this occurred. We also wish to reiterate our offer to meet with the patients and families to apologise in person, and answer any questions they may have."
The DHB was in the process of implementing all the HDC's recommendations and "aimed to have this completed early this year", she said.
She said the external review "assisted us to develop an improvement programme, which we are currently implementing".
Wall said inadequate fetal heart rate monitoring and interpretation was a recurring theme across complaints to the Commissioner, and she was concerned training was not mandatory for all practitioners.
Wall recommended that the DHB consider amending its procedure to ensure that a clinician capable of performing a fetal scalp blood lactate test is rostered on for every shift, and ensure that the lactate testing machine is functioning; and provide HDC with evidence that it has made certain amendments to its clinical practice guidelines and policies.
She also ordered the DHB to provide the commissioner's office with a detailed update report on the steps taken to carry out the external reviewers' recommendations, including in particular recommendations regarding staffing, clinical guidance and training.
