One of England's main abortion providers has suspended terminations under general anaesthetic, and to under 18s, following inspections by healthcare inspectors.
The Care Quality Commission raised concerns about patient safety before Marie Stopes International suspended a number of services.
NHS England said the move would affect around 250 women a week.
However those affected would be diverted to other services.
Following the CQC's inspections of Marie Stopes' services and its corporate headquarters in England, the regulator said it was concerned about poor governance arrangements, leading to what it called "specific immediate concerns" about consent and safeguarding.
It also said it was not satisfied about training and competence for terminations which take place under general anaesthetic or conscious sedation.
Marie Stopes has now decided to:
• suspend termination of pregnancy provision for under-18s and vulnerable groups of women
• suspend terminations under general anaesthetic or conscious sedation
• suspend all surgical terminations at its Norwich centre
Prof Sir Bruce Keogh, national medical director at NHS England, said: "This will be an anxious time for those women affected and we are taking immediate action to ensure everybody involved has access to the appropriate confidential advice and services."
NHS England said it would be helping women to find alternative abortion providers in the meantime.
It has also set up a confidential helpline for anyone with concerns or questions, on 0300 123 1041 (9am to 5pm at the weekends and 9am to 8pm during the week).
Prof Edward Baker, deputy chief inspector of hospitals at the Care Quality Commission, said it was right for Marie Stopes to suspend a number of services.
"At all times, our priority is to ensure that patients get safe, high-quality and compassionate care," he said.
"We believe that the action taken is appropriate to address our concerns."
The CQC said it would continue to monitor the services affected very closely and would not hesitate to take further action, if needed.
It added that it would report fully on its findings once it had published its inspection reports on Marie Stopes in the autumn.
Simon Cooke, chief executive of the abortion service, said it had agreed to suspend some of its termination of pregnancy services to allow the UK arm to "resolve areas of concern in its training and governance procedures".
He said it was working urgently with the CQC and intended to regain full assurance within a few days.
"Alongside this, our immediate priority is to make sure that women booked into one of our affected services are rebooked swiftly into alternative local services and we are working closely with NHS England to ensure that this happens," he added.
Each year 70,000 women are treated within Marie Stopes' centres.