The hospital says it has identified seven sets of birth-related equipment that were cleaned and decontaminated, but not sterilized in a special machine as is normally done.
In a statement, the IWK says it's possible that seven women who gave birth during a six-day period this month received care with the non-sterilized equipment.
However, the hospital says there is a near zero chance of any illness because the equipment had already been decontaminated.
It says all 64 women who were admitted to the birth unit during the period in question are being notified, but no testing, treatment or immunization will be required.
The hospital says it is reviewing its sterilization process as a result and will ensure changes are made to prevent any future errors.