There are 20 stillbirths and six cases in which a baby died shortly after birth are among 43 incidents being investigated by a Welsh health board, it has been announced.

Cwm Taf University health board said a review of pregnancies in which there was an “adverse outcome” since 1 January 2016 had identified 43 cases that needed a full investigation.

The board, which administers health services around Merthyr Tydfil and Rhondda Cynon Taf in south Wales, said it would hire additional staff as concerns were expressed that some incidents had not been properly reported because of staff shortages.

“It’s absolutely key we have appropriate staffing levels to ensure our services are safe,” Prof Angela Hopkins, the interim director of nursing for Cwm Taf, told the BBC.

“We have been very challenged to maintain staffing levels at the optimum level. Some outcomes were not being reported because it wasn’t seen at the time as an issue to report. I’m not saying any of our staff were covering anything up at all. We have excellent staff, they work under tremendous pressure.”

The board said it would recruit 15 more midwives in the coming weeks, as well as appointing a middle-grade doctor and advertising for more medical staff, including consultants. It said it would also appoint a consultant midwife and draw in senior midwives from neighbouring health boards to help.

“It is clear from the recruitment drive that Cwm Taf has embarked on since realising there was a problem that staffing has been an issue in the maternity department,” said Leanne Wood, the Welsh assembly member for Rhondda. “I hope the new appointments and the appointments yet to be made have the impact of turning the department around and relieving the pressure on existing staff.”

'Despairingly lacking': a midwife on support for breastfeeding mothers Read more

She added that the review should be extended to cover a longer period, adding: “I have heard of maternity incidents at the hospital warranting further investigation that go back much further than this limited time frame. To get to the root of the problem, an inquiry needs to be held that gathers up the full facts of the matter.

“I will be writing to the chief executive of Cwm Taf University health board to request that no limits are placed on this investigation and that it delves back as far into the past as it needs to.”

During the period covered by the existing review, which the board said was nearing completion, there were 10,000 births in the region. “Any further information arising from this process will be shared in full with the families concerned and we will provide additional support and any redress as appropriate,” the board said on Thursday.

It added that it had invited representatives of the Royal College of Midwives and the Royal College of Obstetricians and Gynaecologists to conduct their own formal review of the cases.