A medical swab was left inside a woman after she gave birth at King George Hospital in December.
According to a board report for NHS North East London and the City, doctors had delivered her baby using forceps.
The mother suffered “no ill effects” according to the Barking, Havering and Redbridge University Hospitals NHS Trust, which runs the hospital in Barley Lane, Goodmayes.
In a similar incident at Queen’s Hospital in Romford, a swab was left inside a mum-to-be who had cerlage surgery to prevent premature birth in November.
The incidents are one of a government list of “never events” – preventable serious safety incidents that should never happen.
A BHRUT spokesman said: “We take never events very seriously. We have carried out detailed investigations into both of these cases and arranged an external review.
“The women concerned suffered no ill effects and have been fully involved in the investigations.
“Unfortunately this is a persistent problem across the whole of the NHS.
“We are using detailed evidence from NHS London into similar cases across the capital to establish new systems.”
The trust is reviewing processes for swab and instrument counts and improving education and training.
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