2d. No Rotation, Head flexed. —The occiput remains almost invariably behind, but as the uterine contractions are vigorous, the head engages as far as possible, the face having adapted itself to the pubic arch, while the occiput comes in contact with the perineum, and the nucha becomes fixed at the posterior commissure of the vulva. The nucha, that is, the sub occipital region, having become fixed, the uterine contractions gradually force down the face, and the posterior commissure of the vulva being cibly pressed backward, the head emerges by the diameters S. O. M., S.O.F., S. 0. B. The occiput is the last to appear.
3d. No Rotation, Head arrested above the pubes, inter vention nearly always called for. In some cases, spontaneous termina tion. Then, in consequence of the contractions, extension of the head is completed; the chin still remaining fixed above the pubes, the occi put, acted upon by the force of the uterus, traverses the entire posterior wall of the excavation, and first emerges at the posterior commissure of the vulva. As the head is delivered by the trachelo-occipital, trachelo bregmatic, and trachelo-frontal diameters, the forehead emerges last. It is evident that the evolution is much more difficult in these cases, and to render it possible, not only must the uterine contractions be very vigorous, but the foetus must be small, the pelvis at least normal, and the resistance of the soft parts not very great. (Fig. 224.) Sixth Period, Delivery of the I-fwd.—Even under ordinary conditions, although rotation occurs and the head is extended, that is to say, indepen dent of the anomalies above enumerated, the disengagement of the head is sometimes delayed and intervention is called for. The procedure we shall learn hereafter.
Prognosis.—It is evident, that the prognosis of pelvic presentations is much graver than that of vertex presentations.
As to the mother, the first period, that of dilatation, is always pro longed, the more so in proportion as the pelvic extremity is incomplete. The fcet tl parts being elevated and the bag of waters voluminous, the latter often breaks with the beginning of dilatation; and the foetal parts being high up, they do not adapt themselves to the lower uterine segment and dilatation progresses slowly. When the buttocks alone present, the fcetns being bent double, the descent is still more retarded, and when the fatal parts reach the level of the cervix, there is, instead of the hard body formed by the head in vertex presentations, a soft part pressing against the cervix, which likewise contributes to the retardation. It is true, as Cazeaux remarks, that as soon as the cervix is fully dilated, the descent of the breech, trunk, and shoulders is generally rapid, but the head is likely to encounter obstacles and to be arrested at the superior strait. This requires the intervention of the accoucheur, and though it is not dangerous to the mother, it is none the less an intervention. Therefore, we cannot agree
with Cazeaux, who says that, as regards the mother, " in podalic presenta tions, delivery is perhaps more favorable than in those of the vertex." But we fully coincide with him when he adds that " it is certainly more fortunate for her than in face presentations." In our opinion, delivery by the breech is most dangerous to the mother, and we regret that we must differ in this respect from P. Dubois, who considers it more favorable than delivery by the complete pelvic extremity or by the feet. We are pleased to see that our opinion is shared by Tar flier and Chantreuil.
For the child, the prognosis is always grave; so much so that the younger French school, represented by Pinard, Chantreuil and Budin, advises, almost unanimously, to change the pelvic presentation into a ver tex, by external manipulations. We will discuss this opinion hereafter.
But let us add that it is mainly the untimely intervention of the obste trician which renders the prognosis grave, and if in some cases interfer ence is called for, not only must the necessity therefor be recognized, but also the precise moment be known when it is required. In the great majority of cases it is worse than useless, and especially in presentations of the pelvic extremity must the accoucheur know when to remain inac tive. Besides the dangers to which the fcetus is exposed by meddlesome midwifery., there are several others due to the presentation of the pelvic extremity, the greatest of which is undoubtedly compression of the funis.
Yet this compression occurs inevitably at a certain time in pelvic presentations. While in vertex presentations the head, as it comes first, fills the lower uterine segment and passes the cervix and the genital parts, the cord—cases of prolapse excepted—is above this part of the foetus, and thus escapes compression; but this is far from being the case in pelvic presentations. In the latter, after the breech has passed, the funis is necessarily caught in the excavation, at first between its walls and the trunk, later between these and the head. The cord must therefore un dergo compression, which will increase as the labor progresses, because the hardest, most resistant part escapes last. Moreover, the sudden evacuation of the liquor amnii, which occurs in pelvic presentations, tends to draw the cord along, and to make it prolapse in the vagina, where it will be com pressed in proportion to the bulk of the part about to descend. Even without prolapsing, in the strict sense of the word, the funis may be com pressed either between the back of the infant and the uterine wall, or between the fatal parts and the cervix. This compression, however, is generally moderate, and it is particularly during the descent of the head that the dangers of compression become imminent to the infant.