A new mother had a swab left inside her after childbirth at Medway Maritime Hospital, health bosses have admitted.
The item, used to clean and absorb blood, was not found until 20 days after giving birth last October, with medical staff failing to follow the correct procedure.
An NHS report reads: “The investigation found the swab count was documented as being correct but there was no documentary evidence the post-repair swab count was checked with a colleague as per unit guidance.”
Following "missed opportunities" by the woman’s community midwife and GP to discover the swab, it was finally removed in early November.
The patient had an ultrasound scan and a course of antibiotics after the removal, with the incident said to have caused "no lasting harm".
Karen Rule, director of nursing, said: “The investigation has been completed, and we’ve identified the learning we can take from it.
“They hadn’t been using trust-wide recognised checklists.
"That has all been reviewed and updated since, and individual staff have been spoken to and the learning has been shared.”
According to the British Medical Journal, the error can cause fever, infection, pain, secondary postpartum haemorrhage and psychological harm.
It was the first "never event" - patient safety incidents deemed to be "wholly preventable" - to have happened at the Gillingham hospital since November 2017.