The unit at Edinburgh Royal Infirmary (ERI) is closing its door to mothers in labour twice a week, with them having to travel 20 miles to the nearest hospital instead.
The figures, obtained by the Scottish Conservatives, show the unit – which includes six delivery rooms, each with a birthing pool, en suite bathroom and sofa bed – was placed "on divert" on 107 occasions last year.
This led to mothers going to St John's Hospital in Livingston, with ERI's unit closed to non-complex births for between 30 minutes and 12 hours due to a lack of staff or capacity.
NHS Lothian said the number of births diverted away had remained stable in recent years.
The Scottish Conservatives said that in the rest of Scotland, diverting mothers from hospitals had only occurred on "a handful" of occasions. Health spokesman Jackson Carlaw said: "Families across the Lothians deserve better."
NHS Lothian said its new birthing unit had been an "overwhelming success".