The Master of the Rotunda Hospital in Dublin said he hopes that elective and scheduled work can begin again next week but it "makes sense" that appointments are cancelled until then.
Maternity, children and adult services across the board have all been adversely affected by last week's cyber attack on the Health Service Executive's IT systems.
Professor Fergal Malone said the Rotunda is only one of two hospitals in Ireland that is fully digital and there is no way of retrieving old information or saving new information.
Elective gynecology and routine appointments for women who are under 36 weeks pregnant have been cancelled.
Prof Malone said any women in late pregnancy who have ongoing pregnancy challenges or with any concerns, should still come in and said there are contingency plans in place to ensure any abnormal lab results are delivered promptly.
In addition, he said, women experiencing crisis pregnancies will still be seen.
He said that patients will receive all their care in "the very, very near future" and there is no need for patients to seek private care for services.
Meanwhile, the Clinical Director of Children's Health Ireland said urgent day cases or elective admissions will go ahead over the next two days, however outpatients and some elective admissions have been cancelled.
Dr Ciara Martin said routine operations, such as non-urgent scopes, have been deferred for a "week or two", and the ransomware attack means there is no access to previous tests and bloodwork.
She said emergency departments will function as normal, but asked people to only come if there is a real emergency.
Children's Health Ireland (CHI) comprises the three children's hospitals at Tallaght, Crumlin, Temple Street as well as the Paediatric Outpatients and Urgent Care Centre at Connolly Hospital, Blanchardstown.
