SHOULDER DYSTOCIA
Once the fetal head is delivered, natural or assisted breathing must supervene within a few minutes. After (usually difficult) birth of the head, unexpected inability to deliver the shoulders is an obstetric emergency, because the fetal chest remains compressed in the birth canal.
Certain features[1] of the pregnancy should trigger a request for detailed fetal measurements on obstetric ultrasonogram. If macrosomia [large body] is confirmed, elective cesarian section should be planned.
PRACTICE POINT Pregnancy markers anticipating Shoulder Dystocia:
1. maternal obesity
2. clinically large fetus
3. abnormal glucose tolerance
4. postdates pregnancy
If the mother is obese or gains more than 15 kg through the pregnancy, excessive fetal size should be suspected. Gestational weight gain has been shown in a medicolegal study [1a] to be a predictor of permanent neurological injury following shoulder dystocia, but it is not an independent risk factor for shoulder dystocia itself [1b].
Routine plotting on standard charts of length of uterus against number of completed weeks of pregnancy will usually reveal fetal overgrowth. Glucose Tolerance Test is a routine screening test for Gestational Diabetes, which commonly results in an oversize fetus.
Shoulder Dystocia is one of the expected complications when the pregnancy continues more than a week beyond the due date.
Elective cesarian section has been recommended when the estimated fetal weight of diabetic mothers is 4.25 kg or more [1c], but thresholds of 4.5 kg for diabetic mothers and 5.0 kg for non-diabetic mothers are more generally adopted[1d,1e].
Nevertheless, most Shoulder Dystocia resulting in trauma remains unpredictable and unavoidable[2, 2a]. In most cases careful attention to the risk factors will fail to identify the problem. Every obstetrician, whether specialist or general practitioner, must have a clear game plan, because s/he will eventually face this crisis.
Clinical experience[3] continues to validate the recommendations of the authoritative text Williams Obstetrics[4] for Shoulder Dystocia.
PRACTICE POINT Sequential management of Shoulder Dystocia:
1. McRobert's Manoeuvre
2. suprapubic pressure
3. Woods' (corkscrew) Manoeuvre
4. deliver posterior arm
McRoberts described forced flexion of the mother's thighs on lower abdomen, which sufficiently changes the angle of the (bony) pelvis that the fetal shoulders are freed. Pushing down on the lower abdomen may help. Woods in 1943 showed that by progressively rotating the posterior (back) shoulder through 180o the anterior (front) shoulder could be released. Whereas delivery of the anterior arm first is routine, attempts to deliver the posterior may be more successful in Shoulder Dystocia.
The main infant injuries, in order of increasing seriousness, are fractures of collarbone or arm, temporary or permanent brachial plexus damage, and the various consequences of asphyxial brain damage.
Just as causation of obstetric brain damage cannot be assumed (see Medical Litigation News Volume 2, Issue 2), brachial plexus injury may originate from the position of the fetus in the uterus[5]. Nevertheless, if substandard management can be established, proof of negligent causation of permanent asymmetrical paralysis will often follow.
Copyright © 2008 Electronic Handbook of Legal Medicine