This blog will discuss how to recognise the need to intervene to deliver the arms in a vaginal breech birth which has been physiological up until that point. Descriptions are provided as if the woman is in an upright kneeling position, facing away from the attendant midwife or obstetrician. I have been somewhat prescriptive about how delay and dystocia can be evaluated. Experienced practitioners will have their own comfort levels. My intention is to stimulate discussion among modestly experienced practitioners, to help distinguish patterns calling for intervention from those which do not. Once the umbilicus is born, depending on the condition of the baby, unnecessary delay in identifying dystocia could be dangerous.
Recognising what is normal …
Midwives and obstetricians attending vaginal breech births need to learn to ‘read’ what is visible (eg. outside the vagina), as it provides clues about what might be happening at higher levels in the pelvis. In the normal breech mechanisms, the breech descends sacrum transverse, with the fetal back to one side or the other. A rotation occurs as the shoulders engage in the pelvis in the transverse diameter, just as they do in a cephalic birth. The fetal torso fully rotates, finishing fully facing the attendant — “tum to bum.” When this rotation is observed externally, it provides reassurance that the birth is progressing internally. Once the umbilicus is born, there will be a short pause (usually less than 30 seconds) before gravity will begin to pull the unimpeded fetal body down further in the pelvis.
When the shoulders reach the pelvic floor, restitution will occur, just as it does in a cephalic birth. Simultaneously, internally, the aftercoming head is rotating to enter the pelvis in the transverse/oblique diameter, just as it does in a cephalic birth. Externally, this is observed as a slight rotation, in which the anterior fetal arm is released under the pubic arch. Almost immediately (usually less than 30 seconds), another rotation occurs in the opposite direction, and the posterior arm is released under the perineum. This coincides with the final internal rotation of the head, as it realigns to an occipito-anterior position ready to be born, just as it does in a cephalic birth.
A thorough understanding of what is ‘normal’ in a vaginal breech births helps attendants to be aware of when deviations from expected patterns may indicate a threat to fetal well-being. The video below repeats the above information, so that you can recreate it with a doll and pelvis in order to thoroughly understand why this mechanism unfolds in the way that it does.
… and what is not normal.
A deviation from the mechanism described above may indicate a problem, if it is accompanied by a delay. In some cases, when women give birth in upright positions, the combination of a roomy pelvis and the effects of gravity creates a situation in which the fetus can tumble through almost all at once, and the mechanism remains unobserved or seemingly irrelevant to this baby and this mother. If the birth is proceeding rapidly, and the baby is in good condition, there is no need to intervene unless progress stops. Just prepare to break the baby’s fall.
The signal to intervene is an observed variation in the mechanisms, accompanied by a delay (> 30 seconds), unresponsive to spontaneous maternal movement — or any occasion in which the fetus appears compromised. In other words, you observe that descent has stopped and encourage the mother to wiggle, lift a leg, shift her torso, or some other gentle method of shifting the limb which is stuck – but it remains stuck. Some variations suggesting intervention may be necessary include:
The baby has been born to the umbilicus. However, the torso has not completely rotated to face the attendant; the shoulders appear to be in the oblique or A-P diameter of the pelvis. You may need to restore the mechanism. Remember: the shoulders engage in the pelvic inlet in the transverse diameter, visible externally as a complete rotation to face the attendant. If the rotation is not complete, and progress does not resume with spontaneous maternal movement, assume one or both arms are caught up on the pelvic inlet. You can encourage rotation with your hands on the bony prominences of the pelvis (much like Løvset’s), but if this is not easily effective, do not risk twisting the fetal spine. Instead, use ‘prayer hands,’ with your fingertips against the bony prominences of the shoulder girdle, palms flat to avoid fetal organ damage. Elevate slightly to disimpact, and rotate the fetal torso so that the shoulders are in the transverse diameter. Descent should resume following this rotation. Once you have started to intervene, continue to assist the head to be born by manually flexing the head and controlling the delivery, or using shoulder press.
Posterior arm born first
This is not always a problem, but it often happens because the anterior arm is nuchal, eg. raised beside the head. Again, not always a problem. Sometimes an arm in front of the face helps to keep the head flexed, and they can be born simultaneously. If descent and rotation continues, and the baby appears to be in good condition, watch and wait. However, if the posterior arm (closest to the attendant) is born first and there is a delay (> 30 seconds) before the birth of the anterior arm (nearest the symphysis pubis), intervention is likely required. Suspect a nuchal arm, raised alongside the head. Insert your hand behind the fetal back on the side of the arm which needs to be released. Sweep down, in front of the fetal face, and out. This will restore the mechanism and enable the head to descend to the pelvic outlet. If the arm is positioned behind the head and cannot be swept down, rotational manoeuvres may be required, using prayer hands.
One arm born with shoulders in the anterior-posterior (A-P) diameter
Sometimes, the posterior arm is born and the fetus has not rotated at all; the shoulders appear to be in the A-P diameter, with the posterior shoulder visible under the perineum. This is because the anterior arm is nuchal, stretched alongside the fetal head, and prohibiting further descent. It has become wedged tightly against the symphysis pubis, and it is not possible to sweep down in front of the fetal face. This situation will not respond to subtle maternal movements and requires immediate and assertive intervention, in the form of elevation and rotation. In my own experience of using rotational manoeuvres in this situation, I have used ‘prayer hands’ to rotate the fetus into an occipito-posterior position, where it becomes possible to sweep the nuchal arm down in front of the face and out under the pubic arch. The head should be kept in alignment and rotated back to an occipito-anterior position, where shoulder press or manual flexion can be used to deliver the head without delay.
A pause after the birth of the anterior arm, lasting >30 seconds
After the birth of the anterior arm, most of the baby is out. Gravity will usually do its magic, continuing to bring about steady but gradual descent. As the head is rotating into A-P alignment internally, ready to be born, the second arm will release under the perineum. If this process does not resume soon (< 30 seconds) after the birth of the anterior arm, and progress promptly, it suggests two possible problems. Either the posterior arm is blocking the head from descending and rotating, in which case sweeping the second arm down in front of the fetal face should result in both the delivery of the arm and alignment of the head. Or the head has not completely descended into the pelvis. In which case, delivery of the second arm will enable you to get on with assisting the head to be born.
Mechanisms appear normal, complete rotation, umbilicus born, with no further descent for >30 seconds, and especially after the onset of the next contraction
This is when apparent problems with the arms are not actually problems with the arms. The arms are under the sacrum, ready to be born, but they have not been born yet because the head has not entered the pelvis. Although it is possible to sweep them down, this will not solve the underlying problem that the head is extended at the inlet and impacted in the A-P diameter. As described above, the head needs to rotate into the oblique/transverse diameter to enter the pelvis. Begin by lifting the fetal torso to elevate the head off the pelvic inlet slightly. Then rotate to release the arms and enable the head to engage. As you have started to intervene, continue to assist the head to be born, flexing the head manually or using shoulder press once the head has entered the pelvis.
Thank you to Joy Horner, for sharing the photo on which the sketch above is based. And to Mary Cronk, who shared her slides and experience of managing a nuchal arm with me before I encountered it myself, enabling me to resolve it successfully. I am very grateful for the sharing of midwifery knowledge, so I am doing my own sharing in the hope that it will be helpful to another midwife or doctor in a tricky birth.
In this video, the posterior arm is born first, and the obstetrician (Diego Alarcon) gently assists the anterior arm by sweeping it down across the baby’s face.
In this video, the baby is born with the sacrum to the mother’s left and slightly posterior, it looks like due to the positioning of the feet. When the normal rotation to sacral anterior does not occur, the obstetrician (Michel Odent) immediately recognises that the mechanism has deviated from normal and intervenes. He assists the anterior arm to be born by sweeping it down across the baby’s face, restoring the mechanism.