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Determining the position of the fetal head


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FIGURE 2.6.E.1 The fetal skull.


The fetal head normally engages in the maternal pelvis in an occiput transverse position.

With descent, the fetal head rotates so that the fetal occiput is anterior in the maternal pelvis (see Table 2.6.E.1). Failure of an occiput to rotate to an occiput anterior position results in a persistent transverse presentation. Rotation may also occur to an occiput posterior position.

An additional feature of a normal presentation is a well-flexed vertex (see Figure 2.6.E.2), with the fetal occiput lower in the vagina than the sinciput.


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FIGURE 2.6.E.2 Well-flexed vertex presentation.


TABLE 2.6.E.1 Diagnostic features of malpositions and malpresentations


Position

Observations

Picture from introitus

Malpositions

Occiput anterior

On vaginal examination provided that the head is flexed only the posterior fontanelle with three sutures entering it is felt


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Occiput anterior


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Left occiput anterior


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Right occiput anterior

Occiput posterior

On vaginal examination, the posterior fontanelle is towards the sacrum and the anterior fontanelle may be easily felt if the head is deflexed

On abdominal examination the lower part of the abdomen is flattened, and the fetal limbs are palpable anteriorly


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Occiput posterior


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Left occiput posterior

Malpresentations

Brow presentation is caused by partial extension of the fetal head so that the occiput is higher than the sinciput

On abdominal examination, more than half of the fetal head is above the symphysis pubis, and the occiput is palpable at a higher level than the sinciput

On vaginal examination, the anterior fontanelle and the orbits are felt


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Position

Observations

Picture from introitus

Face presentation is caused by hyper-extension of the fetal head so that neither the occiput nor the sinciput are palpable on vaginal examination

On abdominal examination, a large amount of head is palpable on the same side as the back, without a cephalic prominence on the same side as the limbs

On vaginal examination, the face is palpated, the examiner’s finger enters the mouth easily and the bony jaws are felt


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Compound presentation occurs when an arm prolapses alongside the presenting part

Both the prolapsed arm and the fetal head present in the pelvis simultaneously


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Transverse lie and shoulder presentation

The fetus lies in the transverse position with usually the shoulder presenting

On abdominal examination, neither the head nor the buttocks can be felt at the symphysis, and the head is usually in the flank

On vaginal examination, a shoulder may sometimes be felt. An arm may prolapse and the elbow, arm or hand may be felt in the vagina


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Breech presentation occurs when the buttocks and/or the feet are the presenting parts

On abdominal examination, the head is felt in the upper abdomen and the breech in the pelvic brim. Auscultation locates the fetal heart higher than expected with a vertex presentation

On vaginal examination during labour, the buttocks and/or feet are felt; thick, dark meconium is normal


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extended legs flexed legs


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footing a single footing presentation


  

 

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