Shoulder presentation
| Shoulder Presentation | |
|---|---|
 |
|
| A shoulder presentation with a prolapsed arm, by William Smellie | |
| Classification and external resources | |
| Specialty | obstetrics |
| ICD-10 | O64.4 |
| ICD-9-CM | 660.01 |
| MedlinePlus | 002060 |
A shoulder presentation refers to a malpresentation at childbirth where the baby is in a transverse lie (its vertebral column is perpendicular to that of the mother), thus the leading part (the part that enters first the birth canal) is an arm, shoulder, or the trunk. While a baby can be delivered vaginally when either the head or the feet/buttocks are the leading part, it usually cannot be expected to be delivered successfully with a shoulder presentation unless a cesarean section (C/S) is performed.
Shoulder presentations are uncommon (about 0.5% of births) as usually towards the end of gestation either the head or the buttocks start to enter the upper part of the pelvis anchoring the fetus in a longitudinal lie. It is not known in all cases of shoulder presentation why the longitudinal lie is not reached, but possible causes include bony abnormalities of the pelvis, uterine abnormalities such as malformations or tumors (fibroids), and other tumors in the pelvis or abdomen can also lead to a shoulder presentation. Other factors are a lax abdominal musculature, uterine overdistension (i.e. polyhydramnios), multiple gestation, placenta previa, a small fetus, or a fetus with some abnormality. Further, if the amniotic fluid sac ruptures the shoulder or arm may become wedged as a shoulder presentation.
Inspection of the abdomen may already give a clue as it is wide from side to side. Usually performing the Leopold's maneuvers will demonstrate the transverse lie of the fetus. Ultrasound examination delivers the diagnosis and may indicate possible causes such as multiple gestation or a tumor. On vaginal examination, the absence of a head or feet/breech is apparent.
Shoulder presentations are classified into four types, based on the location of the scapula:
While a transverse lie prior to labor can be manually versed to a longitudinal lie, once the uterus starts contracting the uterus normally will not allow any version procedure. A shoulder presentation is an indication for a C/S. Generally, as it is diagnosed early, the baby is not damaged by the time of delivery. With the rupture of the membranes, there is an increased risk of a cord prolapse as the shoulder may not completely block the birth canal. Thus the C/S is ideally performed before the membranes break.
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