• Caesarean section;
  • randomised controlled trial

Please cite this paper as: The CAESAR study collaborative group. Caesarean section surgical techniques: a randomised factorial trial (CAESAR). BJOG 2010;117:1366–1376.

Objective  In women undergoing delivery by caesarean section, do the following alternative surgical techniques affect the risk of adverse outcomes: single- versus double-layer closure of the uterine incision; closure versus nonclosure of the pelvic peritoneum; liberal versus restricted use of a subrectus sheath drain?

Design  Pragmatic, 2 × 2 × 2 factorial randomised controlled trial.

Setting  Hospitals in the UK and Italy providing intrapartum care.

Population  Women undergoing their first caesarean section.

Methods  The interventions were alternative approaches to the three aspects of the caesarean section operation. A telephone randomisation service was used. Surgeons could not be masked to allocation, but women were unaware of which allocations had been used. The analysis was by intention-to-treat, with a prespecified subgroup analysis for women ‘in labour’ or ‘not in labour’ at the time of caesarean section.

Main outcome measures  Maternal infectious morbidity.

Results  A total of 3033 women were recruited. Overall, the risk of maternal infectious morbidity was 17%. For each pair of interventions, there were no differences between the arms of the trial for the primary outcome: single- versus double-layer closure of the uterine incision [relative risk (RR) = 1.00, 95% confidence interval (95% CI) = 0.85–1.18]; closure versus nonclosure of the pelvic peritoneum (RR = 0.92, 95% CI = 0.78–1.08); liberal versus restricted use of a subrectus sheath drain (RR = 0.92, 95% CI = 0.78–1.09). There were no differences in any of the secondary morbidity outcomes and no significant adverse effects of any of the techniques used.

Conclusions  These results have implications for clinical practice, particularly in relation to current guidance on the closure of the peritoneum, which suggests that nonclosure is preferable. The potential effects of these different surgical techniques on longer term outcomes, including the functional integrity of the uterine scar during subsequent pregnancies, are now becoming increasingly important for guiding clinical practice.