There are calls for an investigation into the deaths of babies at two hospitals to be extended.
It comes as Cwm Taf University Health Board said it may have failed to properly investigate historic cases of still birth and neonatal deaths in its maternity units.
It said 43 cases at Prince Charles Hospital in Merthyr Tydfil and Royal Glamorgan hospital in Llantrisant is being reviewed.
The cases include 20 still births and six neonatal deaths between 1st January 2016 and the end of September 2018 and where there was an "adverse outcome" to mothers or their babies.
Leanne Wood, assembly member for the Rhondda has asked the health board to look back further than 2016.
I have heard of maternity incidents at the hospital warranting further investigation that go back much further than that this limited time frame.
The health board says "any further information arising from the review process will be shared with the families concerned and we will provide additional support and any redress as appropriate."
We have gone back and looked at each of these cases in more detail to find out if all appropriate actions were taken at the time.
Health board bosses have called for support from Welsh Government and other health boards. An external review by the Royal College of Midwives and Royal College of Obstetricians and Gynaecologists is planned within weeks.
The health board's chief executive, Allison Williams said: "I have met with senior officials in Welsh Government to discuss the [health board's own] review, its scope and related processes."
Bosses at the board say they have already launched a recovery plan for its maternity services and have cancelled antenatal classes to ensure there are as many staff as possible in the maternity wards.
Professor Angela Hopkins, Director of Nursing and Widwifery at the health board said they have recruited a new consultant midwife and are in the process of recruiting 15 new midwives to ensure services are maintained at a safe level.
Shadow Health Secretary Angela Burns said a thorough review of maternity services across Wales should take place.
The Welsh Government must understand that when it encourages its health boards to centralise its consultant-led maternity services, as has happened in Cwm Taf, they must be able to guarantee the highest levels of patient safety and ensure that measures are in place to properly staff and resource these vital services.
In a statement, the Welsh Government said it is monitoring the situation closely and it is looking at ways it can strengthen maternity services within the health board.
Patient safety is paramount in NHS Wales and our main concern is for the welfare of mothers and babies. They rightly need assurances that urgent action is being taken to ensure services are safe. > We are in regular contact with Cwm Taf to ensure that every necessary action is being taken and are monitoring the situation closely. This includes ensuring that families and staff who have concerns are being supported. We are currently looking at ways we can provide support to strengthen the health board’s maternity service, both in the immediate and longer term. The Health Secretary has spoken with the Chair to discuss his concerns and is considering what further action to take. >