It has long been recognised that breech presentations are associated with increased risks both antenatally and especially at vaginal delivery.
Although breech presentations account for only 3% of all pregnancies they have historically accounted for much more perinatal mortality and morbidity.
Attempts at vaginal breech delivery can be associated with serious complications for the baby at the last moment of delivery. The consensus agreement today is that these pregnancies should be delivered by elective caesarean section.
Breech presentation is the second most common malpresentation.
There are three recognised Breech presentations:
- Frank Breech (extended legs 75%).
- Complete Breech (flexed legs 25%).
- Footling Breech (feet presenting first 1%).
There are a number of potential complications that a Breech presentation may present and these include problems relating to:
- Prolonged pregnancy.
- Prelabour rupture of the membranes.
- Premature labours.
- Inco ordinate uterine activity (poor contractions).
- Prolapsed cord & Complications of delivery.
It has long been recognised that breech presentations are associated with increased risks both antenatally and at delivery.
Delivery of a Breech
It is most important that every one understands that the greatest risk of a breech is the risk of a vaginal breech delivery.
It is vital that one draws a comparison between the birth of a baby with a cephalic presentation and a breech presentation to fully appreciate the essence of the risk.
In cephalic presentations the head undergoes moulding in an effort to try and fit through the pelvis. Moulding takes several hours to develop and often the head will elongate and adopt a shape such that it may fit through the pelvis.
If the head is still too big or the pelvis is too small the head will not fit and obstructed labour will declare itself and an emergency caesarean section will result.
In a breech presentation the soft bottom and abdomen will potentially fit through the pelvis. The fetal head is however the largest part of the baby.
If the fetal head is too large and there is no time for moulding of the head to occur, then the head may obstruct. The entire body, except the fetal head has been delivered and despite an attempt at an emergency forceps this may fail and the baby’s well being and life will be put at risk.
The explanation for this is that the fetal head is not a sphere, it is shaped like an egg. Obstetricians have always known that the short diameters of the fetal head might fit through the pelvis but the long diameters definitely will not.
In the past when breech presentations were often given a trial of vaginal breech delivery, it was a requisite that no effort was to be made to apply traction on the baby’s body in an effort to try and deliver the baby’s head.
We are all aware that the fetal head is pivoted on the spine posteriorly. At the time just before delivery the fetal head is immediately under the symphysis pubis. If traction were applied to the baby at this time this would extend the fetal head on the neck and this would invariably result in extension of the neck.
A much larger diameter of the fetal head would present itself to the pelvis and this would make delivery much more difficult or impossible.
At the time of delivery nobody can know in advance the degree of extension of the fetal head. Given the degree of inaccuracy of ultrasounds in predicting the size of the baby we can also never be too sure of the ultimate fetal birth weight.
In certain circumstances pregnant women will feel completely comfortable that they can deliver a baby with a breech presentation vaginally. That may in fact be the case. Unfortunately the only way that any one can be sure is to “give it a go”. If the labour and delivery go well, all will be fine. If an unexpected problem arises at the last moment the consequence can be very bad.
It is essential that no one should ever gamble on the prospect that everything will be all right with a vaginal breech delivery. We should all practice evidence based medicine. Vaginal breech deliveries have been studied and the evidence is there.
Breech presentations should be delivered by Caesarean Section.