The Greek for childbirth is tokos. And although normal childbirth is eutocia one only hears of the abnormal kind, dystocia. In itself, the word does no more than state there is something wrong, it does not denote the cause of the problem.
Shoulder dystocia is a state in which the shoulder of the fetus impedes delivery. As a general rule, the delivery of the head has commenced, and then there is a turtle sign when the head seems to go back into the birth canal, and everyone in the labor room knows there’s a real problem.
Childbirth is one of those features in life which usually proceed without difficulty, everyone is pleased with what they did and they all congratulate themselves on their skills. But if you spend time in the poorer extremes of the world you find many women give birth unattended with no pre-natal care, no birth attendant, and everything goes just fine. Except for the ones who die with impacted labour. And that’s where the difference lies. The obstetrician really doesn’t add much to the average delivery, but then comes a case when the head starts to go back in and you hope this obstetrician really knows his stuff.
Normally the breadth of the head, between the parietal bones, is the widest part of the neonate, and if the head can widen and pass through the birth canal, the remainder of the child comes sliding after it, with little encouragement needed. However, in circumstances that were not foreseen, the anterior shoulder of the child lying sideways becomes impacted under the mother’s pubis and won’t dislodge.
How often does shoulder dystocia occur?
It happens as often as the doctor in charge of the delivery says it has happened. For medico-legal reasons the doctor may be reluctant to record this event, and if the obstruction was brief, was easily remedied, it might go without record. If the delivery required some specific manoeuvre, however, it almost certainly will be recorded, by the attending nurse if not the doctor. This explains why the incidence is differently reported as somewhere between half to one and a half percent of all deliveries.
What the midwife and nurses can do
A mnemonic is taught and practised in some delivery rooms (labour wards): ALARMER.
A: ask for help, the team of OB specialist, anesthesiologist, resuscitation pediatrician.
L: hyperflex the mother’s thighs
A: anterior shoulder disimpaction
R: Rubin manoeuvre by pressing on the fetus’ shoulder above the mother’s pubis
R: roll mother over so she’s on all fours.
The objectives are to disimpact the shoulder, and to widen the birth canal by posture.
What more the obstetrician can do
Over the centuries a number of extraordinary manoeuvres have been developed to deal with the sad instance of a neonate impacted in the birth canal, and a number of instruments have been devised. The names attached to the ways to achieve disimpaction vary from country to country.
The first urge is to pull on the head to get the child out of there, the face is swelling, going blue and respiratory distress impends in the child that is neither in the womb nor of this world. Heavy traction must be avoided, some traction and some manipulation are accepted practice – and there it’s a question of judgement.
The obstetrician, his hand in the birth canal may push on the posterior shoulder, to free the anterior shoulder from behind the pubis, or he may choose to deliver the posterior arm, ahead of the child, freeing the torso and bringing out the baby. He may also choose to fracture the clavicle (collar bone) thereby narrowing the width of the shoulders – this sounds dramatic but a fractured bone is nothing compared to a dead child.
Surgical manoeuvres are a choice between pushing the child back into the birth canal and extracting it by a Caesarean section, or by opening the uterus (hysterotomy) and pushing the child out through the birth canal, or by dividing the symphysis pubis surgically, widening the canal (much taught in Dublin, safe and effective if you’ve practised it).
There is risk to the child as a whole if not extracted before anoxia supervenes. There is risk to the nerves coming from the neck to the arm, the brachial plexus, which may be stretched or torn, resulting in various patterns of temporary or permanent arm paralysis.
Could this problem with shoulder dystocia have been predicted?
At one time it was clearly stated that the risk of shoulder dystocia was in general not predictable, but there were risk factors of doubtful clinical value: a prior history of delivery with shoulder dystocia, maternal obesity, advanced maternal age, an abnormal pelvis; multiparity, a large fetus (macrosmia) as in diabetes. None of these risk factors bore much weight, and it was calculated that if Caesarean sections were to be performed based on the risk factors, 1000 unnecessary sections would be performed for each permanent brachial plexus injury, and that C sections were not without risk, not to mention cost.
A patented system of making computerised calculations of weight of mother, size of child etc., has been employed (one is always suspicious of patented systems!). The calculation by this system (CALM) were applied retroactively to cases where the shoulder dystocia had occurred and there had been permanent brachial plexus injury to the child, approximately 1-2% of the children delivered who had the dystocia. The results did not suggest such that, using this CALM system, gave a clear benefit that Caesarean section could be proposed with any confidence to the individual to avoid dystocia.