Shoulder dystocia is an obstetric emergency with a potentially adverse outcome. Manouvers other than gentle downward traction are required to complete the birth of the anterior (front presenting) shoulder. The diameter of the fetal shoulders is 12.4 cms and should fit comfortably through the widest diameter of the pelvic brim. Shoulders are flexible enough to allow those of even a larger than normal baby to negotiate the pelvis.
Gibb (1995) described three degrees of shoulder dystocia in order of seriousness:
* a tight squeeze when birthing a big baby the mechanism of labour is normal
* a unilateral (one shoulder) dystocia, where the anterior shoulder has become stuck above the symphysis pubis and the posterior shoulder has entered the pelvis
* a bilateral (both shoulders) dystocia, where both shoulders have arrested above the pelvic brim
This is the first line manoeuvre in most instances of shoulder dystocia, and it has proven to be safe and effective. This manoeuvre is named after William A. McRoberts Jr., a doctor who taught the method in Houston, Texas. The mother lies flat on her back (or with a slight lateral (side) tilt to prevent supine (back) hypotension (low blood pressure). The mother is then assisted into an exaggerated knee to chest position. Once in this position the birth should be able to proceed with the normal birth of the shoulders.
This manoeuvre rotates the symphysis pubis superiorly by approximately 8 cms., and elevates the anterior shoulder. It pushes the posterior shoulder over the sacrum and flexes the fetal spine. It opens the pelvic inlet to its maximum.
All fours position
With a minor degree of shoulder dystocia, movement of the mother may dislodge the obstruction so the shoulders can negotiate the pelvis normally. Assisting the mother into an all fours position can work in this way. This position acts as an upside down McRoberts’ position and carries the same positive effects and will allow the posterior (behind) shoulder to birth first.
The application of suprapubic pressure is intended to adduct and then displace the anterior (front) shoulder away from the symphysis pubis and allow it to enter the pelvis. Pressure is applied using the flat of the hand against the baby’s back in the direction that the baby is facing.
An episiotomy (a surgical incision made in to the thinned out perineum to enlarge the vaginal opening) may be necessary to prevent any further injury to the pelvic floor and perineum during any direct manipulation of the fetus and/or to accomodate the hand of the midwife/obstetrician whilst undertaking direct rotational manoeuvres.
The laws of physics were applied by Woods (1943) to overcome the problem of shoulder dystocia. The woman is placed into lithotomy position (thighs and legs flexed and abducted in stirrups) with the buttocks over the edge of the bed so that there is no restriction to the sacrum or coccyx during the manoeuvre. One hand is applied to the mothers abdomen putting firm gentle pressure onto the fetal buttocks and inserting as much of the hand as is necessry into the vagina to locate the anterior surface of the posterior shoulder (the clavicle). The shoulder is then rotated 180 degrees in the direction of the fetal back which usually causes an abduction of the fetal shoulders. This rotation may dislodge the anterior shoulder and enable the posterior shoulder to enter the pelvic brim.
To achieve the Rubin manoeuvre, a hand must be inserted into the vagina as far as is necessary to locate a shoulder. Then working from behind the fetus, the shoulders are pushed into the oblique (slanted) daimeter. Once the shoulders are in the oblique diameter and free of the symphysis pubis, the birth can be completed.
Occurs where there is a barrier to the passage of the fetus through the birth canal, despite good contrations. Vaginal birth will be mechanically impossible.
Obstructed labour may be suspected if there is little or no progress in labour. On examination, the presenting part (head) remains high and the cervix dilates slowly. As the head is high the cervis is therefore not well applied to it. Recognition of the condition will prevent serious complications.
A cesarean section will be the outcome for an obstructed labour.
Rupture of the uterus is a serious obstetric emergency which can result in fetal and/or maternal death. Uterine rupture thankfully is a rare occurance. Rupture of previous uterine surgery scars including cesarean section scars, is the most common cause of uterine rupture in developed countries. This is influenced by the rising cesarean section rates and the corresponding increase in vaginal birth after cesarean (VBAC). The rate of uterine rupture follwing a lower segment cesarean section is 0.8% (Caughey et. al., 1999).
Complete rupture usually presents with maternal collapse. The mother usually complains of severe and constant abdominal pain, with a reduction or cessation of uterine contractions and vaginal bleeding. A blood transfusion would be needed for severe haemorrhage and/or shock and a hysterectomy would be needed following a cesarean section.
UMBILICAL CORD PROLAPSE
The umbilical cord prolapses through the vagina. This is an obstetric emergency and a “Code Green” emergency caesarean will be called. A general anaesthetic will be administered and surgery will be performed urgently.
Is an obstetric complication in which the placenta is inserted partially or wholly in the lower segment of the uterus. It is one of the main causes of bleeding during pregnancy – antepartum haemorrhage. Placenta praevia’s are graded according to how much of the placenta is covering the cervix. Placenta praevia will require a caesarean section birth.