[Epidemiological aspects of idiopathic early birth (author's transl)].

Epidemiological data of 338 preterm deliveries (excluding multiple gestations) were compared with the same number of term deliveries. Both groups were matched for age and parity. In one third of the cases only, possible organic factors could be attented to preterm delivery. In the remaining patients the etiology was unknown e.g. "idiopathic". These results confirm the difficulty to identify the patient at risk for preterm delivery, especially in the nullipara.