A woman in Canterbury had her last fallopian tube removed unnecessarily because doctors believed it was abnormal, without being sure.
Health and Disability Commissioner Anthony Hill has faulted the Canterbury District Health Board over the 2012 case.
The unnamed woman had already had an ectopic pregnancy, involving a fallopian tube, and had had the tube removed as a result.
When she became pregnant again and a scan indicated a repeat, she agreed to have her last tube removed, but only if it was abnormal.
It was removed and a separate procedure done before it was realised that the tube was normal, as was the pregnancy.
The woman had a termination, however, out of fear the fetus may have been damaged.
Mr Hill said on Monday that extra checks should have been done before removal of the last tube.