Breech presentation has the same probability among medical entities as ‘tails’ in a ‘tossing a coin’ game

Authors


Sir,

The investigation of the probability of an event is one of the basic scientific methods for studying a phenomenon. In medicine, the investigation of the risk of an event may identify its prognosis as well as its aetiology. The article written by Ford et al.1 is significant, because it is one of the few articles dealing with the risk of breech presentation. However, unfortunately, this article does not refer to a published article2 on this topic that provides important notes on the probability of breech presentation, including the recurrence of breech presentation in consecutive pregnancies. Sekulićet al.2 studied the recurrence risk of breech presentation in congenital malformations of the uterus. In cases of multiparity, which were observed at delivery as exclusively breech (BP) or cephalic (CP) presentation, the distribution of these two presentations during the first and second delivery was as follows: CP–CP, 11 cases; CP–BP, 9 cases; BP–BP, 7 cases; BP–CP, 14 cases. The chi-square test did not show a statistically significant difference in the presence of these pairs of presentations (χ2 = 3.47, P > 0.05). This article also studied the probability of breech presentation in all known medical entities for which the incidence of breech presentation is higher than that in the general population, i.e. 3–4%. The results obtained in this study indicate that the probability of breech presentation never exceeds 50%. In a more recent article, Sekulićet al.3 also confirmed that the probability of breech presentation among medical entities is never higher than 50%. These results indicate that breech presentation is not a single consequence of certain medical conditions, but rather a part of a more comprehensive phenomenon. It is a consequence of random filling of the intrauterine cavity, with an equal probability of breech or cephalic presentation. The finding that a certain number of cephalic-presented fetuses assume the presentation for the same reasons as breech-presented fetuses affects significantly the results of studies comparing delivery outcomes in breech and cephalic presentations. The incidence of diseases is therefore similarly increased among both breech-presenting fetuses and fetuses that randomly assume a cephalic presentation. In comparisons of the two presentations, this increased incidence leads to statistical bias that results in underestimation of the difference between the two groups of fetuses. It is therefore necessary to consider these facts in designing future studies of the risk of breech presentation.

Footnotes

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    The authors of the original article were invited to respond to this letter, but declined to do so.

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