Breech presentation and tossing a coin: heads or tails.

Through a retrospective review of our own materials and data from peer-reviewed journals, among medical entities a greater probability than 0.5 was not found for breech presentation. Submitting the occurrence of breech presentation to the classical laws of probability means that each fetus in breech presentation has its 'pair' in cephalic presentation. Among medical entities with a probability of less than 0.5 for breech presentation, the group of fetuses in cephalic presentation consist of two subgroups: (1) fetuses which are by chance in cephalic presentation and whose number is identical to the number of fetuses in breech presentation, (2) fetuses which are in cephalic presentation because of the postural development. Likewise, introducing a medical entity with a small number of cases does not allow a conclusion to be drawn about a relationship between that entity and breech presentation.