18.15 Elective section, ‘trial’ of scar, or section early in labour?

If a mother has had one Caesarean section the alternatives for her next pregnancy are: (1) An elective section, before she goes into labour. (2) Section in early labour. (3) An attempt at vaginal delivery (a ‘trial of scar’). How can you choose between these three?

A lower segment Caesarean section is sometimes done for such conditions as fetal distress, placenta praevia, or the prolapse of the cord or an arm, which are unlikely to happen again in a later pregnancy. When a mother like this becomes pregnant again, there is every reason to expect that her labour will be normal, except for the scar that she now has in her uterus. This will almost always give some warning before it ruptures, so you can safely let her have further attempts at delivering her babies vaginally. This is called a ‘trial of scar’. She can have as many trials as she likes, provided the previous one was successful, but she must have had only one previous Caesarean section. If she has had two sections or more, always section her. Contributors differ greatly in their use of a trial of scar. One only does them in exceptional circumstances.

When you do a trial of scar, admit her to hospital and observe her closely. Should her scar show signs of rupturing, section her immediately. These warning signs only last an hour or two, before her uterus ruptures, so you must admit her and observe her with the greatest care.

Figure 18.19: MEASURING THE TRUE CONJUGATE AT CAESAREAN SECTION. If you pack a steel ruler in the the Caesar set, and measure a patient’s true conjugate routinely, it will help you to decide if a trial of scar is indicated next time she goes into labour. If you do it carefully, it will give you an exact measurement, and will enable you to check the vaginal measurement you made of her her diagonal conjugate when you examined her in the antenatal clinic (it is 2 cm less).A, her uterus has been pushed to the right and the ruler placed across her pelvic cavity. Her bladder has been displaced, partly out of the wound. In reality her symphysis is covered by the lower end of the wound and by her bladder. B, put your finger down behind her symphysis on to its posterior surface, bring your finger and the ruler out together, and see where it comes on the ruler. ‘’ is her true conjugate. Which is it to be?

If CPD was the reason for her Caesarean section, it reduces the chances of a successful trial of scar in this pregnancy, but does not exclude it, because: (1) The pelvis continues to grow up to the age of 25. (2) Uterine action is often poor in the under-16s. An accurate measurement of her true conjugate done at the time of her previous section, as in Fig. 18-16, helps. A trial of scar is unwise if it is <9 cm. It is contraindicated in a breech presentation if the true conjugate is <10 cm. A trial of scar is absolutely contraindicated if her previous Caesarean section was classical.

Good care during a trial of scar means that her pulse must be taken reliably, and you must be able to section her immediately. If, for example, her uterus shows signs of rupturing at 3 a.m., section must be possible before 4 a.m., not at 10 am the following morning. If the organization and discipline of your hospital are not such that it can provide care of this quality, elective section will give her a better chance of saving her baby, her uterus, and perhaps her life. If it takes several hours to find a driver, to fetch you, and to prepare the theatre, a trial of scar will be dangerous. Ideally, a uterus should never rupture during a trial of scar. If more than the very occasional one ruptures, patients should be referred to wait to go into labour at a larger hospital.

Even when conditions are not ideal, a trial of scar may be justified, because the immediate and future risks of a further section can be considerable. If mothers know that they cannot have a trial of scar in hospital, they may try to have trials themselves at home. A mother will usually understand if you say ‟We will give you a try, and if you have any difficulty, we will do another Caesarean section”.

Ask the clinics to refer all mothers who have had a previous Caesarean section, and who are sure of their dates, at 34 weeks, so that you can assess them as described below. If a trial of scar is not indicated, plan an elective section at 38 weeks, or in early labour, if a mother is not sure of her dates.

The best indication that a uterine scar is going to rupture is a rise in her pulse rate. Take this half-hourly. If it rises above 100, or she has pain between contractions, her scar is probably rupturing, so section her. Other signs are described below.

Elective Caesarean sections are one of the alternatives to a trial of scar, but they are not the complete answer: (1) They may not be popular, so find out what your mothers think about them. If they are unpopular, avoid them, but at the antenatal clinic make the decision to section a mother in early labour. (2) Her dates may be uncertain, but even if they are certain, they need to be confirmed by a corresponding fundal height in mid pregnancy, before 20 weeks. (3) She is easily sectioned too early, so that her baby is at risk from prematurity.

HARBANS KAUR (38, gravida 4 para 3) was admitted at 9 a.m. on a Saturday, for a trial of scar, having had one previous Caesarean section with her first pregnancy. She was 7 cm dilated and had good contractions. At noon she was fully dilated and her baby’s head was 3/5 above the brim. During the next half-hour it remained there. The doctor on duty was called for another emergency Caesarean section, so the intern was advised to attempt vacuum extraction. He failed, but in doing so, he included her cervix under the cup, and tore it. At 3 p.m. she developed pain, shock, and abdominal tenderness, and the fetal heartbeat disappeared. She was rushed to the theatre. Her uterus had ruptured, and the tear had extended into her bladder. The superintendent was called. He found that her ureter had been caught in a hastily applied suture. The following day she was found to be leaking urine vaginally. LESSONS. These are many, they include: (1) In multips the second stage should not last longer than 20 minutes. (2) A vacuum extractor was applied when the head was 3/5 above the brim. It should be only 1/5 up or less (except for a trial of vacuum or symphysiotomy). (3) When you apply the cup of a vacuum extractor, you should make sure that you don’t include her cervix. (4) When a trial of scar is done, it must be possible to do an immediate Caesarean section if the trial fails.