An independent investigation has been ordered after swabs were left inside two women who gave birth at the Great Western Hospitals-run maternity unit in Bath.
Both incidents happened last month at the Princess Anne Wing of the Royal United Hospital, which is run by Great Western Hospitals NHS Foundation Trust.
The incidents are medically known as ‘never events’ - serious patient safety incidents that by definition should not happen.
These latest incidents bring the total number of maternity related 'never events' at GWH-run maternity units to four in 2013/14.
The others happened at the Princess Anne Wing at the RUH in April 2013 and the other was at the Great Western Hospital, Swindon, in August 2013.
GWH runs the maternity wing at the RUH along with community maternity services in hospitals including Chippenham and Trowbridge under a contract with Wiltshire Clinical Commissioning Group (CCG).
A statement from GWH said that the incidents involved gauze swabs which were unintentionally left inside the women following natural births.
The swabs were identified by the women themselves and were removed either the same or next day. The statement said no physical harm came to the women.
Hilary Walker, chief nurse at Great Western Hospitals NHS Foundation Trust, said: “We are extremely disappointed and have apologised to the women concerned, who did not come to any physical harm as a result.
"It is completely unacceptable that similar mistakes have been made and we have commissioned an independent investigation to find out why these incidents happened and what needs to be done to prevent them happening again.
"We deliver over 9,000 babies each year across Swindon, Wiltshire and Bath and the vast majority of women receive a high quality of care and have a positive experience of our services.
“As an absolute priority we are reviewing safety systems and procedures and random spot checks are being carried out to ensure they are being followed meticulously. Regular safety briefings and training is also taking place.
“We know that openly and honestly recognising, discussing, and examining mistakes leads to improved patient safety. This is why we encourage staff to report any mistakes, we publish never events and share learning.
"We also have a Being Open Policy and a Duty of Candour to our patients, so when things go wrong, we tell patients and relatives what has happened, apologise and explain what action will be taken.”
NHS England is to host an intelligence sharing meeting between it, GWH and the commissioners of the maternity services to discuss the incidents.
Wiltshire CCG will lead a quality visit to the Princess Anne Wing on April 29.
GWH has run maternity services at the RUH and community maternity units since June 2011 but in January this year it lost out in the re-tendering of the maternity services contract for the RUH and community maternity units.
Wiltshire CCG awarded a three-year contract to the RUH which starts in June.
Ms Walker said: “Great Western Hospitals NHS Foundation Trust and Royal United Hospital Bath NHS Trust are working closely to ensure consistent safe practice during the transition, until Royal United Hospital Bath NHS Trust become responsible for the maternity service at the Royal United Hospital from June.”