For more than two decades the Royal College of Pathologists has raised concerns with the government about the shortage of paediatric and perinatal pathologists.
A report published by the organisation this month found 37% of posts in the UK are lying vacant.
"There are simply not enough consultants to undertake this work and families are suffering," said Dr Clair Evans, the chair of its advisory committee.
The UK has just 52 paediatric and perinatal pathologists and 13 are due to retire in the next five years, according to the Royal College of Pathologists.
Ryan and Amy Jackson founded the Lily Mae Foundation in memory of their daughter who was stillborn at 37 weeks in 2010.
"When we lost Lily we were told it would be a maximum of 12 weeks [for a cause of death] and what we've seen over the years, since then, is it's got longer and longer," said Mrs Jackson.
Her husband added: "When you're in the grief process it's like your world completely slows down, so for us the 12 weeks felt like 12 years."
The baby loss support charity, based in Balsall Common, near Solihull, provides one-to-one bereavement support to families and gives out memory boxes.
They said the delays were a postcode lottery, with some families waiting four to six months and others waiting nine to 12 months.
Mrs Jackson said for those families that did have to wait longer "it's changing that grief journey massively, it's adding a ton of emotions on, and it's extending the time-frame for trying again for another pregnancy".