The foetal presentation refers to how the foetus is situated in the uterus.
The foetal part that is nearest to the cervix is called the presenting part.
When the pregnancy gets to beyond 37 weeks, the foetal head (cephalic) is the presenting part in 97 out of 100 women, and the foetal buttocks (breech) or feet are the presenting part in three out of 100 women.
Although breech presentations are common earlier in pregnancy, the foetuses will usually turn into the cephalic position by themselves.
There are three types of breech presentation:
● Extended or frank breech, in which the foetal buttocks is nearest to the cervix with the thighs against the chest and feet further up near the side of the head, is commonest.
● Flexed breech, in which the buttocks are nearest to the cervix, with the thighs against the chest and the knees bent.
● Footling breech, in which the foetal foot or feet are below the buttocks.
There is no apparent reason for a breech presentation in many instances.
It may well be that the foetus does not turn spontaneously or is most comfortable presenting by the breech (or both).
However, there are factors that are responsible for a foetus presenting by the breech. They include labour prior to 37 weeks; too little or too much amniotic fluid in the sac surrounding the foetus; multiple pregnancy, usually twins; position of the placenta; length of the umbilical cord; and a uterus that has an irregular shape or fibroids, which are non-cancerous tumours of the uterine muscle.
Rarely, a breech presentation may be an indication that the foetus has problems.
In general, a breech presentation has no effect on a baby's long-term health.
External cephalic version
If there is a breech presentation at 36 weeks, the obstetrician will discuss external cephalic version (ECV), which is a procedure used to turn a foetus from a breech or transverse presentation into a cephalic presentation prior to the commencement of labour.
When successful, ECV will make a vaginal birth possible.
The obstetrician will place both hands on the mother's abdomen, one by the foetal head and the other by the buttocks, and then gently push the foetus into a cephalic presentation.
Prior to the ECV, a medication called a tocolytic, may be given to make the uterus relax and prevent uterine contractions from occurring.
There may or may not be discomfort during ECV, depending on the sensitivity of the abdomen, and how the obstetrician presses on the abdomen during the ECV.
Discomfort is more likely if the ECV causes the uterus to contract.
If the foetus appears to be in distress, as shown by a sudden drop in heart rate, the procedure is stopped.
The ECV is monitored throughout the process to ensure that the foetus is not harmed.
Ultrasound examination is initially carried out to confirm the foetal presentation, to locate the placenta, and to assess the amount of amniotic fluid.
It is also often used to check the foetal presentation during the procedure.
The foetal heart is checked before, possibly during, and certainly after ECV.
The methods of checking the foetal heart include the foetal stethoscope, ultrasound, or electronically.
The ECV is stopped if any foetal heart rate abnormalities occur.
The complications of ECV include commencement of labour; separation of the placenta from the uterus (abruption); rupture of the uterus; and damage to the umbilical cord.
Although complications are rare, they do occur. That is why ECV is carried out in a hospital that has facilities for immediate delivery by Caesarean section (CS) should complications occur.
ECV may be attempted at 36-37 weeks when there is only one foetus, which has not engaged in the maternal pelvis, and there is sufficient amniotic fluid.
The ECV is not done if the membranes have ruptured; the mother has a condition which does not permit her to be given tocolytics; a CS is needed, eg placenta praevia in which the placenta covers the cervix; in multiple pregnancy; or there are indications that the foetus may not be well or is known or suspected to have an abnormality.
The success rates of ECV have been reported to be about 60 per cent.
Mode of delivery
Mode of delivery
The mode of delivery is either a vaginal breech delivery or CS, which is a surgical operation in which the foetus is delivered through an incision made in the mother's abdomen.
The pros and cons of either mode of delivery have to be considered.
The management of a vaginal breech birth is similar to that of a cephalic presentation. The choices for pain relief are the same.
During the delivery, the mother will push the baby out of the birth canal to the point where the legs and lower body are delivered.
The baby will be supported by an assistant, and the legs held upwards for the rest of the body to be delivered.
The obstetrician may use some manoeuvres to deliver the shoulders, and/or a forceps to help deliver the baby's head.
A vaginal breech delivery is more challenging as the head, which is the largest part of the foetus, is the last to be delivered, and this may pose problems in some instances.
The Royal College of Obstetricians and Gynaecologists of the United Kingdom supports vaginal breech delivery, provided that the obstetrician is trained and experienced in vaginal breech delivery, there are facilities for emergency CS, if it is necessary, and there are no risk factors present.
A vaginal breech delivery would not be considered if the foetus is a footling breech, large (estimated weight more than 3.8kg), small (estimated weight less than 2.0kg), or has a neck which is tilted backwards; or if the mother had a previous CS, small pelvis or raised blood pressure; or there is placenta praevia.
Attempts at a vaginal breech delivery may still result in a CS if labour is not proceeding satisfactorily, or there is indication of maternal or foetal complications. That is why vaginal breech delivery should only be carried out in a hospital where there are facilities for emergency CS.
The other mode of delivery for a breech presentation is a planned (elective) CS.
The risks of a CS are higher than that of a vaginal breech delivery.
The risks to the mother include infection of the wound and/or the uterus; excessive bleeding, which may require removal of the uterus (hysterectomy); damage to the bladder or the tube that connects the kidney to the bladder; blood clots (thrombosis) in the legs or pelvis (which may be life threatening if part of it dislodges and goes to the lungs - pulmonary embolism); and longer hospital stay.
There are also risks to the baby.
Accidental cuts on the baby's skin when the uterus is incised occur in about two in 100 babies delivered by CS.
The most common risk is that of breathing difficulties, which occur in about 35 in 1,000 babies delivered by CS, compared to five in 1,000 babies delivered vaginally.
Their breathing may be more rapid immediately after birth and the first few days of life (transient tachypnoea). This usually resolves within two to three days.
The risk of the baby's admission to the intensive care unit may also be increased.
There are also risks of anaesthesia to mother and baby.
The risks to mother and baby are usually increased in unplanned (emergency) CS due to problems in labour.
If a patient goes into labour before the planned CS of her choice, the obstetrician will make an assessment about the safety of doing an unplanned CS.
If birth is imminent, it may be safer to have a vaginal breech delivery.
If there is a twin pregnancy with the first foetus in a breech presentation, a planned CS will usually be recommended.
The position of the second twin is not as important as the foetal presentation can change after the birth of the first twin.
A breech presentation does not necessarily mean that a CS will be done. Many women have a vaginal breech delivery without any problems.
A discussion with the obstetrician will assist the patient in understanding the condition as well as the pros and cons of her management options.
The primary consideration must always be the health of both mother and baby.
Dr Milton Lum is a member of the board of Medical Defence Malaysia. The views expressed do not represent that of any organisation the writer is associated with.