There arc so many different reasons for breech presentation that it is impossible to generalize as to whether delivery should be vaginal or by a lower segment Caesarean section. Breech presentation may occur in the presence of a low lying placenta or uterine fibroids or congenital uterine abnormalities. It is particularly common in premature infants and in the second of twins. Any attempt to give a comprehensive review of breech delivery, or even of the part that breech presentation plays in the whole of midwifery, would be doomed to failure.
A baby is perfectly free to move in the uterus and it undoubtedly turns over and over on many occasions until about the end of the 28th or 29th week of pregnancy when it becomes stable in the breech presentation with the head in the fundus of the uterus. Between the 30th and 34th weeks of pregnancy the baby usually turns round to present by the head, but about 3 to 4 per cent fail to do so and remain as breech presentations. When a breech persists, an external cephalic version may be performed. Nevertheless a certain number of babies arrive at term or labour with the breech presenting.
In normal circumstances where the baby is a normal size and the mother’s pelvis is adequate, a breech labour is no more difficult or longer than any other labour, and there are no increased difficulties after the delivery. The real problem in breech presentation is not the breech delivery of the small baby through a normal pelvis, but a mechanical problem concerning the delivery of a large baby, or of a normal baby with an extended head, or when the mother’s pelvis is small. Any factor that slows the delivery may lead to lack of oxygen. Any factor that forces the -delivery to be hurried may cause injury to the baby.
The head is the largest part of the baby. When the head presents it is the first part of the baby to descend through the cervix and also through the pelvic cavity. The head will mould and flex, thus reducing its diameter by more than i cm., and its passage through both the cervix and the pelvic cavity, which takes several hours, is accomplished in slow, gradual and very easy stages. In a breech presentation the head does not have time to mould and flexion is always incomplete resulting in the presentation of much larger head diameters. Furthermore, the baby’s pelvis is smaller than the head so that the largest part of the baby has to be delivered at the end of the labour. The head has to travel the entire distance from above the brim of the pelvis to the outside world in approximately 7 minutes or less because as soon as the head enters the pelvic brim the umbilical cord is squeezed between the bones of the head and the pelvis and the baby’s oxygen supply is cut off. If delivery is too slow, taking more than 7 minutes, then the baby will suffer from lack of oxygen.
It is a very simple mechanical problem. If the baby’s head is normal in size and the mother’s pelvis is normal in size, the baby’s head may travel through the pelvis quite easily and naturally without any trouble. If, however, the baby’s head happens to be slightly larger than normal, or is not well flexed, or if the mother’s pelvis happens to be a little smaller than usual, it will take too long for the head to be delivered in its own time and, on the other hand, if the baby’s head is delivered too quickly it may be injured.
The answer to the problem of breech delivery is that every instance, every woman and her baby, are judged on their own merits. Various precautions are taken to ascertain whether mechanical difficulties are likely to arise during a vaginal delivery and if the obstetrician is satisfied that there will be none, the breech delivery is allowed to proceed normally. When a woman has already had a good sized baby it is known that she has a ‘favourable pelvis’ and therefore the risk from breech delivery is minimal. On the other hand there are many obstetricians who believe that a Caesarean section is the most convenient and safest method of delivery, and this should be accepted philosophically without any feeling of having been ‘robbed of the delights of childbirth’.
Labour begins in breech presentation exactlyy as it does in a cephalic presentation. However, should the membranes rupture spontaneously before the onset of labour the woman is immediately admitted to hospital without waiting for uterine contractions-to begin.
Labour proceeds normally and the first stage of labour lasts the usual length of time. At the onset of the second stage the woman is placed in the lithotomy position. During the second stage the breech descends slowly through the pelvis. The mother is usually told not to push, letting the breech descend under the power of uterine contractions alone. Spontaneous descent indicates that the remainder of the delivery will be smooth, straightforward and satisfactory. If the breech does not descend spontaneously through the pelvis it may be decided, even at this very late stage, to perform Caesarean section.
The passage of meconium by the baby in a breech labour may not be a sign of foetal distress, as it usually is in cephalic presentation. The baby’s anus and lower bowel are being squeezed continuously throughout labour so that the meconium is forced out automatically.
When the baby’s buttocks distend the perineum an episiotomy is performed. Uterine contractions will then proceed to deliver the baby’s buttocks, legs and abdomen as far as the umbilicus when the doctor gently pulls down a short loop of umbilical cord to prevent tension on it during delivery when its upper part will be trapped between the baby’s head and the mother’s pelvis. The baby’s arms and shoulders are then delivered. The modem method of completing the delivery is by forceps so that the baby’s head can be delivered steadily and gently without any hurry and without any possibility of damage or injury. A local anaesthetic is usually given before this is done.
After the baby’s head has been delivered, the cord is divided in the usual way and the third stage of labour is conducted quite normally.
Breech extraction is the delivery of a breech baby by applying traction and pulling on the lower limbs. This is not now performed except in very special circumstances and usually only when a second twin happens to present in a difficult manner.