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.
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."
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.
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.
Any families with concerns can contact Cwm Taf health board on 08000 328999 or email CTHB_concerns@wales.nhs.uk