A manual of obstetrics . curred, and the capacity ofthe maternal pelvisis large and the ex-pulsive forces arepowerful, nature willdispose of even theseimpacted shoulderpresentations by aprocess known asspontaneous evolution(Figs. 126-129). Bythis term is meantthe unaided occur-rence in childbirth ofa series of changeswhereby a shoulder is transformed within the pelvis into a complex presentation—either of the breech andthe shoulder or of thehead and the thorax—and delivery finally ef-fected. This, of neces-sity, is of rare occur-rence, and is possibleonly under the com-plexus of circumstancesj
A manual of obstetrics . curred, and the capacity ofthe maternal pelvisis large and the ex-pulsive forces arepowerful, nature willdispose of even theseimpacted shoulderpresentations by aprocess known asspontaneous evolution(Figs. 126-129). Bythis term is meantthe unaided occur-rence in childbirth ofa series of changeswhereby a shoulder is transformed within the pelvis into a complex presentation—either of the breech andthe shoulder or of thehead and the thorax—and delivery finally ef-fected. This, of neces-sity, is of rare occur-rence, and is possibleonly under the com-plexus of circumstancesjust enumerated. Thereare two varieties of spon-taneous evolution de-scribed—namely, that inwhich the breech is delivered first, which is most fre-quent, and that in which the shoulder first emerges,followed by the head and thorax, the child being doubledup upon itself {corpore condiiplicato vcl rcdnplicatd); thelatter is of extremely rare occurrence. The mechanismsof these two phenomena are as follows: (i) Of spon-. FiG. 127.—Spontaneous evolution, second stage. 464 A MANUAL OF OBSTETRICS.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectobstetrics, bookyear1
