A hospital has been told not to take on any new student midwives until May, following an investigation into the deaths of 10 women.
The hospital says improvements have been made
The Nursing and Midwifery Council has refused approval for Northwick Park Hospital, north-west London, to take on new trainees, until its next visit.
The current 35 trainees will be allowed to continue, and the hospital says improvements have been made.
The NMC wants to check they continue once it is taken off special measures.
The Healthcare Commission was called in to investigate maternity services last year - after concerns were raised about 10 deaths in three years.
There are about 5,000 births at the hospital each year. In the UK an average of one woman in 8,700 dies during childbirth.
A team of doctors and midwives was also sent in to the unit to improve things.
It was put on special measures and the NMC visited to assess its "learning environment".
Now an NMC report has refused approval for any more trainees to be taken on, until it can assess the situation when it next visits in May, months after the maternity unit is taken off special measures.
Christina McKenzie, head of midwifery, said a lot of work had been done and staff and students were positive about the investigation.
But she added: "The NMC will have to conduct a further visit before we can be reassured that the learning environment at the trust is appropriate for more student midwives."
In a statement, North West London Hospitals NHS Trust said it was opening an "integrated midwife-led birth centre" and taking on an extra consultant midwife to focus on low-risk normal births - an area the NMC felt its trainees did not get enough exposure to.
Trust chief executive Mary Wells said they had focussed on improving maternity services and a refurbished maternity unit would open in a few months.
"We will use the time the NMC have given us before the next intake of student midwives to ensure that we do provide the most supportive environment for our trainees," she added.
"We look forward to training more students in the future."