Birth before arrival in hospital.

In a series of 35,466 booked patients, the incidence of birth before arrival in hospital (BBA) was one in 695 (0.14%). These labours were usually precipitate (71%), and 51% of them occurred in the patient's first or second pregnancy. Most BBAs were avoidable (65%) had the patients attempted to reach hospital at the onset of labour. A patient need not be concerned about the possibility of BBA if she presents for assessment when she believes that labour has begun.