Caesarean Section and Trial of Scar
Authors: Targett Christopher 
Published: February 2008

EDITORIAL COMMENT: The writer of this review has analysed the details of the patients having Caesarean sections at the Mercy Maternity Hospital over a period of 18 years and has written the chapters on Caesarean section and Trial of Vaginal Delivery following Caesarean section in all of the Triennial Clinical Reports of the Mercy Maternity Hospital, Melbourne. This detailed review of the literature and consideration of the Mercy Maternity Hospital data show that there is no simple answer to the selection of patients for trial of scar, and whether or not it is safe to use oxytocin to induce or enhance labour, with or without epidural analgesia, in such patients. The incidence of uterine rupture varies in different series. Because of the increasing Caesarean section rate, the recent literature contains many references to trial of scar, but as the writer points out, it is necessary to pay more attention to the indications for primary Caesarean section, if the total Caesarean section rate is to be contained. It would seem more sensible to practise a policy of programmed labour with enhancement of uterine activity with oxytocin in nulliparas, than to be radical in the management of patients who have a uterine scar and whose first Caesarean section was indicated by cephalopelvic disproportion. Since a discussion with the patient will entail telling her the odds of a trial of scar being successful, her opinion on whether she wishes to have another labour as well as a Caesarean section if the trial fails must influence treatment, and she will opt for elective Caesarean section if she regards the chance of vaginal delivery to be unacceptable. The variation from one centre to another in the incidence of trial of scar in patients with a previous Caesarean section is so great (25%‐75%) that the obstetrician's opinion must influence the patient's decision. It is also salutary to note that some of the series with the highest incidences of trial of scar in patients having had a previous Caesarean section, also have some of the highest incidences of successful vaginal delivery, without an unusually high incidence of uterine rupture! There are many intangibles of obstetric judgement in the obstetric finesse of trial of uterine scar.

Summary: A retrospective study over a 16‐year interval at the Mercy Maternity Hospital was made to analyse the contribution made by repeat Caesarean to the overall Caesarean section rate. The practice of trial of scar was examined with reference to the selection of patients, the conduct of labour, and the risks incurred by the mother and infant. The literature has been reviewed.

The overall Caesarean section rate was 13.1% with 39.1% being repeat Caesarean sections. The primary rate has increased from 6.6% to 9.3% while the incidence of repeat Caesarean has increased from 2.7% to 6.8%. Of the 4,892 patients with one or more previous Caesarean sections, 1,577 (32.0%) were allowed a trial of scar, 1,197 (75.9%) of whom achieved a vaginal delivery. Thirteen patients sustained a ruptured uterus (0.82%) and 2 of the infants died (perinatal mortality 0.13% due to this complication alone).

To ensure the greatest chance of vaginal delivery with optimum safety, it is suggested that the onset of labour should be spontaneous, and the issue should be resolved within 12 hours, A decrease in the number of Caesarean sections may be achieved either by reducing the number of primary Caesarean sections, and/or encouraging more patients to attempt a trial of scar. These options are preferred to pushing a trial of scar beyond the limits of common sense.