The choice between a trial of vaginal birth or elective caesarean section

1. A trial of vaginal birth or elective caesarean section?
The most common questions in pregnancy are often related to delivery, such as ‘can I achieve an uncomplicated vaginal birth?’ or ‘should I try vaginal birth or opt for an elective caesarean section instead?’

Traditionally, a trial of vaginal birth is believed to be the right way unless there is medical complication. This belief is not without legitimate reasons. However, a certain proportion of women might have significant fear of childbirth (see the part on ‘Maternal fear associated with pregnancy and childbirth’) that they would consider elective caesarean section as an alternative.

To answer the question, it is important to have a basic understanding of the pros and cons of the different modes of delivery. Of course, the final decision has to be individual, taking into consideration of each pregnant woman’s special circumstances.

2. The reasons for a trial of vaginal birth

  • Natural- from the biological and evolution points of view, vaginal delivery is the natural method of childbirth for almost all mammals;
  • High successful rate- from the statistical point of view, at least 80-85% of low-risk women who go for a trial of labour can achieve a successful vaginal delivery;
  • Shorter hospital stay- typically 3 days’ hospitalisation in Hong Kong;
  • Quicker postpartum recovery- this is especially true for the subsequent deliveries;
  • Pave the way for future- following one vaginal birth, the subsequent vaginal deliveries will be much easier. This is a very important factor for those who plan for more than one child;
  • Avoidance of a tummy scar- although complications related to caesarean section are low nowadays, hypertrophic or keloid scar may not always be preventable;
  • Low risks of wet lung syndrome- the stress of labour and the birth process help the baby to expel the fluid out of the lungs;
  • Maternal fetal microbiome- babies born vaginally acquire the maternal vaginal flora from the birth canal. It is now believed that these bacteria are beneficial for the immune system and the bowel system of the infants.

3. The drawbacks of a trial of vaginal birth

  • Trauma- vaginal birth may be associated with vaginal or perineal wound, either due to tears or a cut (episiotomy). The pelvic floor muscles might also be disrupted. Vaginal delivery is a risk factor for genital prolapse in a long run;
  • Failure- following a trial of vaginal birth, a small proportion will need emergency caesarean section either because of failure of progress of labour, abnormal fetal heart tracing or less commonly, maternal complication. Emergency caesarean section is associated with a higher risk of complications compared with an elective caesarean delivery, especially wound infection;
  • Fetal risks- labour process poses stress to the unborn fetus. Healthy fetuses find this stress advantageous as it helps them to expel the lung fluid more efficiently at birth. However, some fetuses cannot withstand this stress and show signs of fetal distress. Very uncommonly, some fetuses suffer from birth asphyxia;
  • Labour pain- labour pain can be excruciating. While various methods of pain relief are available, some women might still find the pain debilitating (see the part on epidural analgesia for more advice on pain relief)

4. The pros of an elective caesarean section

  • A better control- for a planned caesarean delivery, the timing is scheduled and all family members may have better preparation. It also avoids the uncertainties regarding failure of vaginal birth, trauma and fetal risks;
  • Minimal operative risks- major operative complications related to caesarean section are uncommon nowadays;
  • Good pain relief- caesarean sections are performed under spinal anaesthesia nowadays and the pain relief is excellent. The post-operative pain control has also improved and under experienced team, women should not have too much pain even in the post-operative period; 
  • Immediate skin-to-skin contact- the pregnant women are fully conscious throughout the operation. Immediate skin-to-skin contact with the baby and breast feeding are possible. The practice of exclusive breast feeding is usually not a problem with caesarean delivery nowadays;
  • Fetal risks- avoidance of the risks of intrapartum hypoxic damage to the unborn fetus
5. The drawbacks of an elective caesarean section
  • Longer hospital stay- typically 5 days’ hospitalisation in Hong Kong;
  • Operative morbidity- while the operative complications are uncommon in Hong Kong, they can still happen.
  1. (i) Wound infection is the most common one, in the order of 2-5%;
  2. (ii) Operative blood loss might be more compared with vaginal delivery but usually blood transfusion is not required;
  3. (iii) Bladder injury can happen in 0.1-0.2% of cases;
  4. (iv) Thrombo-embolism (a clot in the major vein of the lung) is a rare but serious medical condition, which might be more common following caesarean section compared with vaginal delivery;
  • Neonatal wet lung syndrome- the lack of stress of labour might be associated with a poorer ability of expulsion of the fluid from the lung by the baby upon delivery. It is called ‘transient tachypnoea of newborn’. The affected baby shows difficulty with breathing and the oxygen saturation in blood might be low. Treatment is by oxygen therapy and it usually takes a few days to recover. Babies delivered vaginally can also develop this but are less common compared with elective caesarean section;
  • Future pregnancies- the major drawback of an elective caesarean section is on the subsequent pregnancies and deliveries:
  1. (i) Higher chance of rare complications including scar pregnancy and placenta accreta (morbid adhesions of the placenta to the uterine wall);
  2. (ii) A trial of vaginal delivery following one caesarean section is considered possible but it carries a small risk of rupture of the caesarean scar at the uterus (0.5-1%);
  3. (iii) Higher chance of caesarean section in subsequent pregnancies. There might be intra-abdominal adhesions with each caesarean section which can pose difficulty with the subsequent operation;
  4. (iv) The post-partum recovery time will be roughly the same as the first caesarean delivery. It will not be getting quicker and quicker as in the case of vaginal deliveries

6. Can we predict the chance of successful vaginal delivery?

A successful and easy vaginal delivery with good pain relief is obviously the ideal on balancing the pros and cons of the 2 modes of deliveries. Yet, if one can predict a long difficult labour ending with emergency caesarean section or even worse, an urgent caesarean section due to fetal distress, one would choose an elective caesarean section instead! The question is: can a successful vaginal delivery be accurately predicted?

The answer is ‘Yes’ and ‘No’.

There are favourable factors for successful vaginal delivery, including young age, roomy pelvis, lack of pregnancy complications, soft and lax cervix at term, and for the fetus, smaller baby, head engagement into the mother’s pelvis and head facing down. On the contrary, older mother, short stature, unfavourable and firm cervix, bigger baby, high floating fetal head in the mother’s tummy at term are predictors for high chance of failure.

The difficulty is that the labour process is very complex and governed by the interplay of a variety of factors. One crucial factor is the efficacy of the uterine contractions in pushing the fetus down the birth canal. This cannot be predicted before the onset of labour. What we do know is that those who have delivered vaginally before usually will have efficient uterine contractions in the subsequent deliveries. However, for the first-time mother, it is not possible to predict precisely.

Hence, we can predict only to a certain extent. Even for those with a lot of unfavourable factors, successful vaginal delivery may still be possible if they have a trial. Therefore, it is always a weigh balance between the pros of a successful vaginal delivery versus the risks and the price to pay in the process of the trial.  

7.Does the woman have a choice? 

Delivery is one of the most unforgettable experience the couple could have. It is therefore very important to make preparation for it. The mode of delivery should always be the choice of the couple. It is the job of the obstetricians and midwives to provide data to fit their individual needs so that they can make a wise choice for themselves.

This article is contributed by Dr. T.N. Danny Leung
Updated on 25.09.2020