Description, Causes and Risk Factors:
Arrest of normal labor after delivery of the head by impaction of the anterior shoulder against the symphysis pubis.
Shoulder dystocia occurs when, after delivery of the fetal head, the baby's anterior shoulder gets stuck behind the mother's pubic bone. If this happens, the remainder of the baby does not follow the head easily out of the vagina as it usually does during vaginal deliveries.
This simple definition of shoulder dystocia, however, glosses over many complexities. For example, should a delivery be categorized as involving shoulder dystocia only when there is some time delay -- 60 seconds is often suggested in this context-between the delivery of a baby's head and shoulders? Or is shoulder dystocia present any time that a delivering physician finds that the shoulders cannot be delivered with the normal amount of downward traction on the fetal head? Some have suggested that the definition of true shoulder dystocia requires that an obstetrician had to perform special maneuvers in order to deliver the shoulders.
Exactly how shoulder dystocia is defined is more than just a semantic issue. It sets the parameters for the collection of statistics related to shoulder dystocia, a necessity for research aimed at decreasing shoulder dystocia related injuries. It also determines when a baby's injuries might be attributed to a physician's actions during labor and delivery.
A pregnant woman may be at risk for shoulder dystocia if:
She has diabetes.
She is pregnant with more than one baby.
She is obese.
She delivers after the baby's due date.
She has had shoulder dystocia or a very large baby during a past delivery.
Her baby is very large. (But in most cases of shoulder dystocia, the baby's weight is normal. And for most very large babies, shoulder dystocia doesn't occur).
Although the incidence range promulgated by ACOG is 0.6-1.4%, the incidence of shoulder dystocia varies in the literature by a factor of 50, from 1 in 750 to 1 in 15 deliveries. One reason for this wide variation is in part the variation in denominator or specific patient population (eg, all births vs only vaginal births vs only term vaginal births) used to calculate incidence. However, the primary reasons for incidence variation are difficulty in diagnosis and underreporting because the condition is most often mild and resolved without untoward outcome.
Based on a host of retrospective studies, most incidence ranges vary from 1-2% of cephalic vaginal deliveries. Although few in number, prospective studies examining shoulder dystocia incidence among vaginal deliveries generally report higher values, from 3.3-7%. These higher values among 2100 vaginal cephalic deliveries within the few prospective studies likely reflect the more accurate incidence among the at-risk population (vaginal, cephalic deliveries of at least 34 weeks' gestation).
One often described feature 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.
There is no objective diagnosis for shoulder dystocia.Milder forms of the condition are difficult to diagnose, or are often uneventful and uncoded.Although the textbook definition is clear, the obstetric provider cannot visualize the obstruction clinically. Two commonly accepted diagnoses are as follows:
The need to perform ancillary maneuvers to complete delivery.
More than customary traction needed to deliver the fetal trunk.
Since "customary traction" varies from clinician to clinician, the diagnosis is inherently subjective.
Management of shoulder dystocia primarily involves repositioning the laboring patient or repositioning the fetus.
Proper management of shoulder dystocia is the key to solving the impaction problem without untoward outcome. About a dozen techniques can be broadly divided into 2 categories-fetal maneuvers (where the manipulation is directly upon the fetus within the birth canal) and maternal maneuvers (where the primary manipulation is on the mother-often done by ancillary personnel).
Five maneuvers (Rubin, Jacquemier, Woods, and McRoberts maneuvers, and suprapubic pressure), either singly or in combination, accomplish delivery nearly 100% of the time. The others are used less commonly or resorted to only after primary ones have not accomplished delivery. Recent research has demonstrated there are fewer brachial plexus injuries when fetal maneuvers are employed as the initial maneuver.
Complications from shoulder dystocia are many. Maternally, postpartum hemorrhage can result from uterine atony caused either by overdistention from fetal macrosomia and/or dysfunctional contractility caused by mechanical obstruction. Another complication is third or fourth degree perineal laceration or extension of episiotomy. Since episiotomy is not necessary for most shoulder dystocia deliveries, this complication may be avoidable; however, fetal size alone may cause these extensive lacerations. Although immediately reparable in the delivery room, potential long-term maternal consequences include wound breakdown, fistula formation, dyspareunia, and fecal incontinence.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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