In a small percentage of births, the baby’s shoulder will become locked under the mother’s pubic bone immediately after delivery of the head. The doctor or midwife may be unable to deliver the baby with the usual hand skills. Every doctor and midwife is trained in the handling of this emergency, and there are several different approaches.
Occasionally, the baby is injured during the process to free the captured shoulder. The most common injury is a stretching and tearing of the nerves of the baby’s arm. Although most of the these injuries resolve without future problems, occasionally the damage to the nerve is permanent and results in weakness or paralysis of the arm. Less frequently, the collarbone (clavicle) or upper arm bone (humerus) are broken in an attempt to free the shoulder.
Shoulder dystocias are almost always associated with big babies. However, the majority of big babies are born without involving shoulder dystocia. There is also a relationship between shoulder dystocia and labor protractions and arrests……..especially those which lengthen the duration of Second Stage (after the cervix is dilated).