Depression of the posterior vaginal wall is needed with constant and firm pressue on the head. Symphysitomy carries the danger of long-term maternal morbidity. The bladder must be catheterised, the legs and hip supported by assistants and a solid bladed scalpel divides the symphysis from above whilst the urethra is displaced laterally. The angle between the legs should not exceed 80 degrees, as this places excessive strain on the sacroiliac joints and can tear the anterior vaginal wall and urethra. Although half of all shoulder dystocias occur during delivery of infants weighing less than 4kg, the incidence is poportional to birth weight.
Prolonged pregnancy increases the risk of SD by a factor of two.
Interventions unlikely to significantly reduce incidence of shoulder dystocia Induction of labour for postmaturity - most cases of SD do not occur in prolonged pregnancy and fetal weights are not markedly reduced when such a policy is adhered to. Most cases of SD occur in infants of average weight. Click here for the Word 7 formatted version of this hand-out.