Plain English Summary
Background and study aims
The number of cesarean sections (CS) continues to increase in industrialized countries. In Canada, for example, the percentage increased from 21.2% to 26.3% between 2000-2006. Over 30% of CS’s are performed because the mother has had one for a previous pregnancy. Every year, over 30,000 women who have undergone a CS in the past will be faced with a difficult choice for their next pregnancy, that is, whether they should plan for a second CS or have a trial of labor (TOL) and try for a vaginal birth after cesarean (VBAC). One significant but rare risk of a VBAC is a uterine rupture (rupture of the womb). The uterine rupture is a obstetrical emergency and is the main complication associated with a TOL. However, although having a second cesarean delivery may help prevent uterine rupture in most cases, it carries with it a higher risk if both maternal and perinatal (just before and just after birth) complications. Repeat CS is now considered routine treatment for mothers who have had a CS in the past and health professionals hesitate, due to medical-legal risk, to recommend a TOL in the absence of a validated and effective method that can predict the chances of a successful VBAC and the risk of uterine rupture. The PRISMA program, includes a professional training program from the Society of Obstetricians and Gynaecologists of Canada to standardize intrapartum (childbirth) management for a TOL. It includes a decision aid tool to support women’s decision making in the choice of the mode of delivery (DAT), an estimate of the risk of uterine rupture using ultrasound measurement of lower uterine segment (LUS) thickness (MSI) and an estimate of the chance of VBAC success. The aim of this study is to test whether the PRISMA program will reduce the rates of major complications during childbirth for mothers who have had a previous CS.
Who can participate?
Pregnant women who have had one prior CS at a participating center where the newborns were at least 22 weeks and weighed at least 500g at point of delivery.
What does the study involve?
Participants are grouped according to level of care and then randomly allocated into one of two groups, intervention or control. Participants in the intervention group are asked to fill-out a decision aid tool about how they want their baby to be delivered. Their physician then estimates their chance of VBAC success during the pregnancy and at the time of the admission for delivery and estimates their risk of uterine rupture, using abdominal and transvaginal ultrasound measurement of LUS thickness between 35 and 38 weeks. The physician and the woman then decide together how the baby should be delivered. Participants in the control group receive usual care. Assessments include any adverse effects on the mother or child during or just after birth and the number of successful VBACs.
What are the possible benefits and risks of participating?
Women will have access to clinical tools that will facilitate the choice for a TOL or an elective repeat cesarean delivery. In addition, women will have a third-trimester ultrasound and will be informed of their risk of uterine rupture, in order to determine if they can attempt a safe vaginal delivery. There is no anticipated risk, abdominal and transvaginal ultrasounds are painless and present no risk for the woman or the baby.
Where is the study run from?
Hospital of Laval University (Canada)
When is the study starting and how long is it expected to run for?
September 2015 to September 2019
Who is funding the study?
Canadian Institutes of Health Research
Who is the main contact?
Professor Nils Chaillet
Process for decision-making, obstetrical RISk management and Mode of delivery After a prior cesarean delivery in Québec (PRISMA): a multicentre, two arms, randomized cluster trial
1. Primary hypothesis
The PRISMA program will result in a reduction in the rate of major perinatal morbidity among the hospitals following the intervention compared to control hospitals. The trial will have the power to detect a relative reduction of 25% in the rate of major perinatal morbidity between groups
2. Secondary hypotheses
This program will result in:
2.1. A reduction in major maternal morbidity
2.2. A reduction in both minor maternal and minor perinatal morbidity
2.3. An augmentation in the Vaginal Birth After Cesarean rate
University Laval Regional Ethics Board, 09/12/2015, ref: MP-20-2016-2718
Multicentre stratified, cluster randomized, parallel-group trial
Primary study design
Secondary study design
Cluster randomised trial
Patient information sheet
Not available in web format, please use contact details to request a participant information sheet
Choice of mode of delivery among women with one prior cesarean delivery
1. Intervention group hospitals:
1.1. A tool to assess the woman a priori intentions for a trial of labor or an elective repeat cesarean delivery
1.2. An estimate of the risk of uterine rupture using ultrasound measurement of lower uterine segment thickness
1.3. An estimate of the chance of success of trial of labor using demographic and patient factors with a validated decision aid (Grobman nomogram)
1.4. A professional training program from the Society of Obstetricians and Gynaecologists of Canada to standardize management of women with one prior cesarean delivery and intrapartum management for a trial of labor
2. Control group hospitals:
2.1. Usual care
Primary outcome measure
1. Major perinatal morbidity measured at the mid and at the end of the 2-years intervention period.
This composite outcome includes:
1.1. In utero, intrapartum and neonatal death, defined as the fetal death in utero, during labor or as the newborn death at less than 28 days of age (excluding lethal congenital abnormalities)
1.2. APGAR score at 5 mn < 4
1.3. Metabolic acidosis (umbilical arterial pH < 7 + base excess ≤ -12 mmol/l)
1.4. Major trauma (skull fracture, subdural / subarachnoid haemorrhage, brachial plexus injury, spinal-cord injury, major genital injury, paresis/paralysis at discharge)
1.5. Intracerebral / Intraventricular haemorrhage (grade 3 and 4)
1.6. Periventricular leukomalacia
1.7. Seizure (occurring from delivery to discharge)
1.8. Invasive mechanical ventilation with endotracheal intubation
1.9. Major respiratory morbidity (BPD : neonatal bronchopulmonary dysplasia treated with oxygen or ventilation at 36 weeks post-menstrual age or at 28 days of life, PPHN : Persistent Pulmonary Hypertension of the Newborn, Pneumothorax, Pulmonary haemorrhage, Hyaline membrane disease requiring mechanical ventilation)
1.10. Necrotising enterocolitis (NEC) - (stage 2 and 3)
1.11. Hypoxic-ischemic encephalopathy (APGAR 5mn < 4 + pH < 7 + base excess < -12 mmol/L + seizure)
1.12. Proven neonatal sepsis/infection (positive blood or cerebrospinal fluid culture)
1.13. Hypotension requiring vasopressor support
2. Data will be collected every day from women and neonatal clinical records during the 3.5 years of the program in the 40 hospitals (20 control and 20 interventions), to compare major perinatal morbidity in the intervention group with the rate in the control group at the end of the 2-years intervention period (year 3 and 4).
3. In the primary intention-to-treat analyses, we will assess the effect of the intervention on the rate of major perinatal morbidity using the multivariable generalized-estimating-equations extension of logistic regression, with an exchangeable covariance matrix, to account for the clustering of women within hospitals.
4. Changes in the risk of major perinatal morbidity in the two study groups between the 1-year baseline (preintervention) period and the 2-years intervention period will be compared with the use of an adjusted odds ratio (with 95% confidence intervals) for the interaction between group (intervention vs. control) and time period (intervention period vs. baseline).
5. The adjusted odds ratio for interaction will be estimated with the use of data on women who will deliver during the baseline period or the intervention period and will measure the intervention effect with the difference-in-differences approach, which is adapted for generalized-estimating equations analyses of clustered binary outcomes.
Secondary outcome measures
Measured at the mid and at the end of the 2-years intervention period
1. Major maternal morbidity rate
2. Minor perinatal morbidity rate
3. Minor maternal morbidity rate
4. Vaginal Birth After Cesarean rate
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Public hospitals with functional surgical rooms and high performance sonographic devices.
2. More than 300 deliveries per year
3. Written agreement to participate in the study from the directors of maternity services and professional services
Woman level (data collection):
1. All women with one prior cesarean delivery who delivered at participating centers and whose newborns had a gestational age of at least 22 weeks and weighed at least 500 g at delivery.
Target number of participants
40 hospitals in Québec (around 24 500 women with one prior cesarean delivery)
Participant exclusion criteria
1. Public hospitals with, at the time of recruitment, recent or ongoing quality-improvement programs specifically designed to target women with one prior cesarean delivery
Woman level (data collection):
2. Women that give birth or abort before 22 weeks of gestation
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Hospital of Laval University (Centre hospitalier de l'Université Laval (CHUL))
2705, Boulevard Laurier
CHU de Québec Research Center
Mother-child center CHUL (Centre mère-enfant du CHUL)
CHU de Québec
Canadian Institutes of Health Research
Instituts de Recherche en Santé du Canada, CIHR
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
1. Publication and oral presentation in high impact journals and international conférences
2. Training program PRISMA available at the end of the intervention for the hospitals from the control group
3. Plan to implement the PRISMA program throught Canada and others countries with our partners if the program is effective
4. Plan to develop a sonographic training platform at the Université Laval for ultrasound measurement of lower uterine segment thickness
Intention to publish date
Participant level data
To be made available at a later date
Basic results (scientific)