The Royal Free Hospital will not be penalised after staff lost a log containing the confidential medical details of up to 78 pregnant women.

The Information Commissioner’s Office (ICO), the data protection watchdog, confirmed this week that it will take no further action after investigating the incident.

A midwife lost an appointments diary in May which contained details of visits by 78 women to antenatal clinics between January and May this year.

It included names, phone numbers and addresses, along with medical information for “some” of the patients, although the hospital, in Pond Street, Hampstead, could not say how many.

One patient contacted the Ham&High at the time to say the episode had been very stressful for her.

She said: “They have no idea who’s got it [the log] now and it’s just not good enough.”

The hospital referred the matter to the ICO and made contact with the women affected.

An ICO spokesman this week said no action would be taken, but a record will be kept in case something similar happens again at the Royal Free.

He said: “Before deciding whether further action was required we considered a number of factors including the nature of the personal information disclosed, the existing measures the [hospital] had in place to keep patients’ information secure and the remedial action taken by the organisation following the incident, including its decision to contact all of the individuals affected.

“After considering all of these issues we decided that no further action was required on this occasion.

“We will keep a record of the incident and may revisit it again if similar compliance issues come to our attention.”

The ICO can issue fines of up to £500,000 for serious breaches of data protection and privacy regulations.