The other adverse event fatality was a "placental abruption resulting in foetal demise".
No further details were provided on those two deaths.
Adverse events are overseen nationally by the Health Quality and Safety Commission, which defines them as events with negative reactions or results that are unintended, unexpected or unplanned.
The commission says adverse events are often referred to as incidents or reportable events and in practice, are most often understood as events which result in harm to a consumer.
Debbie Brown, the Bay of Plenty District Health Board's senior advisor of governance and quality, said: "Over 62,000 patients are discharged from our hospital sites each year and when a person has an adverse outcome as a result of their care with the BOPDHB it is regrettable."
She said when care did not go as planned the district health board thoroughly reviewed it and worked closely with patients' family through that process.
"We then implement any resulting recommendations, to ensure no other person and their family/whānau has the same experience."
The incident involving the elderly inpatient was investigated and found to be "an unfortunate accident and therefore no further recommendations were made".
The placental abruption case is currently under review and the findings are not yet available.
Brown said nationally the number of adverse events reported to the Health Quality and Safety Commission in 2017/18 rose compared to the previous years.
"This increase is likely due to changes in requirements for reporting along with better reporting within DHBs. Even with increased reporting the adverse events numbers at the BOPDHB for 2017/18 have come down from 2016/17."
The Bay of Plenty District Health Board area had 15 adverse events in 2016/17.
Meanwhile, there were a total of 15 mental health events resulting in death or serious harm over a period of 18 months in the district health board area – 13 community and two inpatient.
Fourteen of those 15 cases resulted in a death.
The district health board would not comment on the mental health cases and would not clarify details about the figures it provided.
There were also seven "Always Report and Review Events" in 2017/18.
This is a new category for preventable events which, regardless of whether any harm has occurred, should be reported and reviewed in the same way as an adverse event.
Where to get help
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111. Or if you need to talk to someone else:
Lifeline: 0800 543 354 or text HELP (4357) for free (available 24/7)
Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
Youthline: 0800 376 633 or text 234
Kidsline: 0800 543 754 (available 24/7)
Whatsup: 0800 942 8787 (Mon-Fri 1pm to 10pm. Sat-Sun 3pm-10pm)
Depression helpline: 0800 111 757 or text 4202 (available 24/7)
Rainbow Youth: (09) 376 4155
Samaritans: 0800 726 666
Need to talk? Call or text 1737
