The occipitoposterior position is perhaps the most common and important abnormality in the mechanism of vertex presentations, occurring in approximately 25 per cent of all such presentations. Its management has long been a matter of discussion. Although the literature on the subject is voluminous and facts of some value have been derived from it, there will undoubtedly be many more contributions, for there will always be a posterior.
The occipitoposterior position is probably much more common than is generally supposed. I am convinced that many prolonged labors supposedly occipitoanterior were occipitoposterior in the beginning. The reported incidence varies greatly: Tweedy and Wrench1 reported 121 cases in 15,167 deliveries (0.8 per cent); Williams,2 11.3 per cent in 5,000 cases; Scott,3 14.04 per cent in 1,000 consecutive cases; Piper,4 17.1 per cent; Danforth,5 25.1 per cent in 1,131 private deliveries. In an earlier paper6 I reported
HENNESSY JP. OCCIPITOPOSTERIOR POSITION. JAMA. 1943;123(9):524–528. doi:10.1001/jama.1943.02840440006002
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