The position of the human fetus during pregnancy and the probability of spontaneous rotation to the vertex position in primi and multiparae

Abstract

Now that ultrasonography is a routine examination in pregnancy, breech presentations are frequently diagnosed. On the basis of 4066 individual examinations a graph was drawn indicating the relative frequency of breech, vertex and transverse presentations in the course of pregnancy. There are clear, and in some cases statistically significant differences between primiparae and multiparae with regard to the individual presentations. The analysis of several ultrasonographic examinations of one and the same patient makes a prediction possible of the likelihood of the foetus moving from breech to vertex presentation in a particular week of the pregnancy. Here there are clear differences between primiparae and multiparae: thus, the chance that a foetus in breech presentation in the 29th week will move spontaneously into vertex presentation in a primipara is 31.1%, while the degree of probability in multipara is 70.2%. In the 33rd week the probability is 15.5% in primiparae, as opposed to 57.5% in multiparae. From the 37th week on, spontaneous movement into vertex presentation is no longer likely to occur, in either primiparae or multiparae. In the 29th week, on the other hand, the likelihood of a foetus in vertex presentation moving into breech presentation in a primiparae is 0.6%, while in a multiparae it is considerably higher, at 2.3%. From the 33rd week on there is no likelihood of spontaneous movement into breech presentation in either group. Two tables, for primiparae and multiparae, respectively, show the likelihood of movement from one presentation to the other between the 13th and 41st weeks.(ABSTRACT TRUNCATED AT 250 WORDS)