|Classification and external resources|
Shoulder dystocia is a specific case of obstructed labour whereby after the delivery of the head, the anterior shoulder of the infant cannot pass below, or requires significant manipulation to pass below, the pubic symphysis. It is diagnosed when the shoulders fail to deliver shortly after the fetal head. Shoulder dystocia is an obstetric emergency, and fetal demise can occur if the infant is not delivered, due to compression of the umbilical cord within the birth canal. It occurs in approximately 0.3-1% of vaginal births.
Signs and symptoms
One characteristic of a minority of shoulder dystocia deliveries is the turtle sign, which involves the appearance and retraction of the fetal head (analogous to a turtle withdrawing into its shell), and the erythematous (red), puffy face indicative of facial flushing. This occurs when the baby's shoulder is obstructed by the maternal pelvis.
About 16% of deliveries where shoulder dystocia occurs will have conventional risk factors.
There are well-recognized risk factors, such as diabetes, fetal macrosomia, and maternal obesity, but it is often difficult to predict. Despite appropriate obstetric management, fetal injury (such as brachial plexus injury) or even fetal death can be a complication of this obstetric emergency.
Maternal Risk Factors: . Age >35 . Short in stature . Small/Abnormal pelvis . Term+ (post dates) (more than 42 weeks gestation) . High maternal birthweight (macrasomia - >4000g) . Diabetes (2-4 fold increase in risk)
Factors which increase the risk/are warning signs:
- the need for oxytocics
- a prolonged first or second stage of labour
- turtle sign
- head bobbing in the second stage
- failure to restitute
- No shoulder rotation or descent
- Instrumental delivery
Recurrence rates are relatively high (if you had shoulder dystocia in a previous delivery the risk is now 10% higher than in the general population).
Management of shoulder dystocia has become a focus point for many obstetrical nursing units in North America. Courses such as the Canadian More-OB program encourage nursing units to do routine drills to prevent delays in delivery which adversely affect both mother and fetus. A common treatment mnemonic is ALARMER
- Ask for help. This involves preparing for the help of an obstetrician, for anesthesia, and for pediatrics for subsequent resuscitation of the infant that may be needed if the methods below fail.
- Leg hyperflexion (McRoberts' maneuver)
- Anterior shoulder disimpaction (pressure)
- Rubin maneuver
- Manual delivery of posterior arm
- Roll over on all fours
The advantage of proceeding in the order of ALARMER is that it goes from least to most invasive, thereby reducing harm to the mother in the event that the infant delivers with one of the earlier maneuvers. In the event that these maneuvers are unsuccessful, a skilled obstetrician may attempt some of the additional procedures listed above. Intentional clavicular fracture is a final attempt at nonoperative vaginal delivery prior to Zavanelli's maneuver or symphysiotomy, both of which are considered extraordinary treatment measures.
Courses that teach procedures include ALSO and PROMPT. A number of labor positions and/or obstetrical maneuvers are sequentially performed in attempt to facilitate delivery at this point, including :
- McRoberts maneuver; The McRoberts maneuver is employed in case of shoulder dystocia during childbirth and involves hyperflexing the mother's legs tightly to her abdomen. This widens the pelvis, and flattens the spine in the lower back (lumbar spine). If this maneuver does not succeed, an assistant applies pressure on the lower abdomen (suprapubic pressure), and the delivered head is also gently pulled. The technique is effective in about 42% of cases
- suprapubic pressure (or Rubin I)
- Rubin II or posterior pressure on the anterior shoulder, which would bring the fetus in an oblique position with head somewhat towards the vagina
- Woods' screw maneuver which leads to turning the anterior shoulder to the posterior and vice versa (somewhat the opposite of Rubin II maneuver)
- Jacquemier's maneuver (also called Barnum's maneuver), or delivery of the posterior shoulder first, in which the forearm and hand are identified in the birth canal, and gently pulled.
- Gaskin maneuver, named after Certified Professional Midwife, Ina May Gaskin, involves moving the mother to an all fours position with the back arched, widening the pelvic outlet.
More drastic maneuvers include
- Zavanelli's maneuver, which involves pushing the fetal head back in with performing a cesarean section. or internal cephalic replacement followed by Cesarean section
- intentional fetal clavicular fracture, which reduces the diameter of the shoulder girdle that requires to pass through the birth canal.
- maternal symphysiotomy, which makes the opening of the birth canal laxer by breaking the connective tissue between the two pubes bones facilitating the passage of the shoulders.
- abdominal rescue, described by O'Shaughnessy, where a hysterotomy facilitates vaginal delivery of the impacted shoulder
The major concern of shoulder dystocia is damage to the upper brachial plexus nerves. These supply the sensory and motor components of the shoulder, arm and hands. The aetiology of injury to the fetus is debated, but a probable mechanism is manual stretching of the nerves, which in itself can cause injury. Furthermore, excess tension may physically tear the nerve roots out from the neonatal spinal column, resulting in total dysfunction. The ventral roots (motor pathway) are most prone to injury, as they are in the plane of greatest tension (anterior, sensory nerves are somewhat protected due to the usual inward movement of the shoulder).
- Klumpke paralysis
- Erb's Palsy
- Fetal hypoxia
- Fetal death
- Cerebral palsy
- Maternal post partum hemorrhage (11%)
- Vaginal lacerations and 3rd/4th degree tears, extended episiotomies
- uterine rupture
Although the definition is imprecise, it occurs in approximately 0.3-1% of vaginal births.
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