An investigation is under way to establish why rates of conception at an NHS fertility treatment unit are falling, which has seen patients transferred to a private hospital.
Some services at Glasgow Royal Infirmary have been temporarily relocated to the city's Nuffield Hospital while NHS Greater Glasgow and Clyde works to establish if there is an "identifiable reason" for the decrease.
Initial inquiries showed no clinical reason for the drop, the health board said. The investigation was launched after a fall was recorded in the anticipated success rate over the previous two months at the assisted conception service in November.
Around 25 NHS patients per week are now temporarily receiving fertility treatment at the private hospital.
The health board said: "We were unable to identify a cause for this decrease. However, a full internal investigation has been undertaken. Through our initial investigations, it appears that the decrease in success rates are not as a result of clinical standards at the unit.
"As we continue to try and establish if there is an identifiable reason for the decrease we took the decision to enact our contingency arrangements and temporarily transfer part of the assisted conception service to the Nuffield Hospital in Glasgow who are fully licensed providers.
"We took this action at a very early stage to ensure the highest clinical standards and minimal disruption for our patients while we try to ascertain a cause or causes for the very recent decline in success at our Glasgow Royal Infirmary-based unit."
The laboratory and theatre element of the service transferred last month but outpatient clinics remain at Glasgow Royal Infirmary. Some medical, nursing and other clinical staff from the unit are also working with Nuffield staff to treat NHS patients.
Dr Helen Lyall, consultant gynaecologist at the Royal Infirmary's assisted conception service, said the decision to relocate some services was based on putting patients first.
"Assisted conception success is never guaranteed but we must make sure that every chance possible is given to every single one of our patients," she said. "The Glasgow assisted conception service is recognised as an excellent unit, achieving higher-than-national-average success rates."