Condition category
Pregnancy and Childbirth
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Not provided at time of registration

Trial website

Contact information



Primary contact

Prof Peter Brocklehurst


Contact details

National Perinatal Epidemiology Unit
University of Oxford
Old Road Campus
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

International study of caesarean section surgical techniques: a randomised fractional factorial trial and follow-up study



Study hypothesis

Study hypothesis amended as of 02/08/2007:
The CORONIS Trial aims to evaluate alternative surgical techniques for five specific aspects of caesarean section technique in a large pragmatic randomised controlled trial, to help determine which methods lead to an optimum outcome for women and their infants.

During the trial development phase it was known as the International CAESAR study.

Ethics approval

1. Oxford Tropical Research Ethics Committee (OXTREC), 05/03/2007, ref: 013-06
2. Follow-up study: OXTREC,17/11/2010, ref: 013-06

Study design

Multicentre factorial randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Information leaflet in English for main trial and for the follow-up study


Pregnancy and Childbirth


There are five pairs of interventions being tested; however, each participating hospital will only take part in three of these five possible comparisons. The interventions being compared are:
1. Blunt versus sharp abdominal entry
2. Exteriorisation of the uterus versus intra-abdominal repair
3. Single versus double layer closure of the uterus
4. Closure versus non-closure of the peritoneum (pelvic and parietal)
5. Chromic catgut versus Vicryl for uterine closure

Intervention type



Drug names

Primary outcome measure

Current information as of 29/09/10:
Death or maternal infectious morbidity (one or more of the following: antibiotic use for maternal febrile morbidity during postnatal hospital stay, antibiotic use for endometritis, wound infection or peritonitis) or further operative procedures; or blood transfusion of >1 unit of whole blood or packed cells.

Initial information at time of registration:
Death or serious maternal morbidity (one or more of the following: antibiotic use for maternal febrile morbidity during postnatal hospital stay, antibiotic use for endometritis or wound infection; further operative procedures on the wound; blood transfusion).

Secondary outcome measures

All within six weeks of delivery unless stated otherwise:
1. Death
2. Febrile morbidity
3. Endometritis
4. Wound infection treated with antibiotics
5. Operative procedures on wound
6. Pain
7. Blood transfusion
8. Interventions used for severe primary Post-Partum Haemorrhage (PPH)
9. Stillbirth after trial entry
10. Apgar score less than three at five minutes
11. Laceration of baby at time of caesarean section
12. Death of the baby by six weeks of age
13. Other severe maternal morbidity
Health service utilisation:
1. Duration of operation (from incision to closure)
2. Duration of hospital stay post-caesarean section
3. Duration of stay in Intensive Care Unit post-caesarean section
4. Number and duration of re-admissions to hospital within six weeks of the caesarean section

Added as of 13/03/2013: Follow-up Study Outcomes
Women’s health and mortality
1. Following the CORONIS birth and before any subsequent pregnancy, any new onset or worsening of:
1.1. pelvic pain
1.2. dysmenorrhoea
1.3. deep dyspareunia
1.4. urinary symptoms of poor stream and/or frequency which did not respond to antibiotics
2. Diagnostic laparoscopy or diagnostic laparotomy (not related to pregnancy)
3. Hysterectomy or tubal/ovarian surgery (not related to pregnancy)
4. Bladder or bowel damage in those women who have had surgery, excluding diagnostic laparoscopy and diagnostic laparotomy (not related to pregnancy).
5. Following the CORONIS birth, any new onset of:
5.1. abdominal hernia
5.2. bowel obstruction
6. Woman’s death
Reproductive status
7. Number of women with no subsequent pregnancy
7.1. Voluntary infertility
7.2. Involuntary infertility
8. Use of fertility treatments
Subsequent pregnancies
9. Number of women having any subsequent pregnancy and for these women, the following outcomes will be measured:
9.1. Inter-pregnancy interval from the CORONIS birth to the end of the subsequent pregnancy
(regardless of loss or birth)
9.2. Miscarriage of the pregnancy subsequent to the CORONIS birth
9.3. Ectopic pregnancy
9.4. Gestation at delivery (by best estimate) of the first viable pregnancy (gestational age > 24 or >28 weeks depending on country specific definition)
9.5. Stillbirth
9.6. Neonatal death
9.7. Mode of delivery:
9.7.1. Non-instrumental vaginal
9.7.2. Instrumental vaginal
9.7.3. Pre-labour caesarean section
9.7.4. In labour caesarean section
9.8. Other pregnancy complications including: uterine rupture, uterine scar dehiscence, placenta praevia, morbidly adherent placenta, abruption, postpartum haemorrhage requiring transfusion, severe infection within 6 weeks postpartum, hysterectomy up to 6 weeks postpartum, manual removal of placenta,
9.9. Bladder or bowel damage at the time of subsequent caesarean section
CORONIS children – morbidity and mortality
10. Death or serious morbidity of the child who was born at the time of CORONIS participation (Although no difference in death is expected, there is likely to be a time difference
between ‘sharp’ and ‘blunt’ abdominal entry and this may, in theory, lead to more neonatal
encephalopathy which may lead to a greater risk of later death).

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

Women will be eligible for trial entry if they are undergoing delivery by lower segment caesarean section through a transverse abdominal incision.

Note: women are eligible if they have had no previous, or one previous, caesarean section. Fever in labour is not a contra-indication to trial entry.

Added as of 13/03/2013: All women recruited into the CORONIS Trial and eligible for three year follow-up will have a health assessment conducted by a study assessment doctor.

Participant type


Age group




Target number of participants


Participant exclusion criteria

Women will not be eligible for trial entry if there is clear indication for a particular surgical technique or material to be used, that interferes with any of the allocated interventions, e.g. in a previous vertical incision.

Recruitment start date


Recruitment end date



Countries of recruitment

Argentina, Chile, Ghana, India, Kenya, Pakistan, Sudan

Trial participating centre

University of Oxford
United Kingdom

Sponsor information


University of Oxford (UK)

Sponsor details

Clinical Trials and Research Governance Office
Manor House
John Radcliffe Hospital
United Kingdom

Sponsor type




Funder type

Research council

Funder name

Medical Research Council (UK) (Grant ref: G0500959)

Alternative name(s)


Funding Body Type

government organisation

Funding Body Subtype

National government


United Kingdom

Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

2007 protocol in:
2013 results in:
2014 follow-up protocol in:
2016 3-year follow-up results in:

Publication citations

  1. Protocol

    The CORONIS Trial. International study of caesarean section surgical techniques: a randomised fractional, factorial trial, BMC Pregnancy Childbirth, 2007, 7, 24, doi: 10.1186/1471-2393-7-24.

  2. Results

    Abalos E, Addo V, Brocklehurst P, El Sheikh M, Farrell B, Gray S, Hardy P, Juszczak E, Mathews JE, Masood SN, Oyarzun E, Oyieke J, Sharma JB, Spark P, Caesarean section surgical techniques (CORONIS): a fractional, factorial, unmasked, randomised controlled trial, Lancet, 2013, 382, 9888, 234-248, doi: 10.1016/S0140-6736(13)60441-9.

  3. Protocol

    Abalos E, Oyarzun E, Addo V, Sharma JB, Matthews J, Oyieke J, Masood SN, El Sheikh MA, Brocklehurst P, Farrell B, Gray S, Hardy P, Jamieson N, Juszczak E, Spark P, CORONIS - International study of caesarean section surgical techniques: the follow-up study, BMC Pregnancy Childbirth, 2013, 13, 215, doi: 10.1186/1471-2393-13-215.

  4. Results

    CORONIS collaborative group, Caesarean section surgical techniques: 3 year follow-up of the CORONIS fractional, factorial, unmasked, randomised controlled trial, Lancet, 2016 , doi: 10.1016/S0140-6736(16)00204-X.

Additional files

Editorial Notes

10/05/2016: Publication reference added. 13/03/2013: the following changes were made to the trial record, in order to include details of the follow-up study: 1. The public title was previously "International study of caesarean section surgical techniques: a randomised factorial trial". 2. The overall trial end date was changed from 30/09/2011 to 30/06/2015. 3. The target number of participants was updated from 15,000 to 15,729.