A senior midwife leading an investigation into baby deaths has warned it is unlikely the full extent of the scandal will ever be known.
Donna Ockenden said it was unlikely records more than two decades old would be accessible to the inquiry into maternity failings at Shrewsbury and Telford Hospital NHS Trust.
But she vowed she would strive to get answers for families affected.
One mother said the inquiry “has to be done once and done right”.
Writing in The Independent, Ms Ockenden said: “It is important that families understand that the further back in time we go, the less likely we are to be able to access health records since health records in the NHS are routinely kept for 25 years.
“After that time it is unlikely we will be able to access records.
“Please be assured, however, that your story will be heard and we will continue to try and get you the answers you deserve.”
The trust is being investigated over a number of deaths of babies and mothers.
A leaked report by maternity expert Ms Ockenden outlined a catalogue of maternity failings from 1979 to the present day that led to avoidable deaths of mothers and babies at the trust.
It is believed more than 800 people have now raised concerns about their care.
Then health secretary Jeremy Hunt ordered an independent inquiry into maternity failings at the trust in 2017.
Rhiannon Davies, who pushed for the investigation after her daughter Kate died at the trust in 2009, said: “Donna is very clear that she won’t conclude the review for another year, which is fine, because yes, it has to be done once and done right.”
Ms Ockenden said more families had come forward to speak to the inquiry, and she urged others to tell their story.
She added: “From the outset, my priority has always been the welfare of every family who may have concerns about the maternity care they received at the trust.
“By the time I complete my report at the end of 2020, I want to make sure we have done all we can to reach every family who has raised concerns.
“It may be that we have already reached all the families we need to, but I just want to make doubly sure there are no more families who want to be heard.”
The trust’s interim chief executive Paula Clark has previously offered her “unreserved apologies” to families and said there had been a “sea change” in the culture at the trust.
Follow BBC West Midlands on Facebook, on Twitter, and sign up for local news updates direct to your phone.