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Patricia Janssen, PhD School of Population and Public Health Faculty of Medicine University of British Columbia

In 2011, the cesarean birth rate in � Canada reached 27.1%, 29% in Ontario and 30.7% in British Columbia. Increasingly, women are faced � with the choice to plan a vaginal or cesarean birth after a previous cesarean birth. SOGC Guidelines recommend that � planned vaginal birth be offered to women with one previous transverse low-segment cesarean.

In 2011 Among � women with a previous cesarean birth, the rate of repeat cesarean birth was 81.7% in Canada.

In all Health Authorities in BC, the principal predictor of CS is previous CS Chi Square test for model fit

Wen et al. 2004, Canada. n=300,000. � Uterine rupture 0.65 vs. 0.25 per 100,000 � women for TOL vs CS. Guise et al. 2010, US. Systematic � review n=402,000. Maternal mortality- 0.013% vs. � 0.004% for elective repeat CS vs TOL. Perinatal mortality -0.13% vs. 0.05% � for TOL vs. elective repeat CS Smith et al. 2002, Scotland. Meta- � analysis, n=313,328. Perinatal death 12.9 v. 1.1 per 10,000 for � TOL vs. CS

Mercer et al. 2008. US, n= 13,532. � Significant decrease in the rate of uterine rupture (0.87% vs. 0.45%), for planned vaginal births after at least 1 prior vaginal birth. Zelop, 2000. US. n=3,783. Prior � vaginal birth was associated with one fifth of the risk of uterine, 0.2 % vs. 1.1%. Hendler, 2004. US. n=2,204. No � difference in the rates of uterine rupture, 0.5% vs. 1.5%.

Design � Retrospective cohort study using � data from the BC Perinatal Data Registry for 2000–2008. Inclusion � 1or 2 prior CS, singleton fetus, � cephalic presentation, term Exclusion � Gestational hypertension, pre- � existing diabetes, cardiac disease excluded.

Relative risks of planned vaginal vs. � CS calculated using Poisson regression with robust error variance. Absolute differences or � attributable risk (AR) reported. Number needed to treat (NNT) or � harm (NNH) calculated as the inverse of the AR. > 80% power to detect an � absolute difference of 1.0% in our composite outcomes, type I error 0.05, 2-sided.

LIFE THREATENING NON LIFE THREATENING � DVT � Uterine dehiscence � Pulmonary embolism � Surgical wound infection � Amniotic embolism � Puerperal infection or sepsis � Uterine rupture � Hysterectomy � Non-life threatening � Surgical procedure to control complications of anesthesia intrapartum or postpartum bleeding � Blood transfusion � Septic embolism � Pulmonary, cardiac or CVS complications from anesthesia

LIFE THREATENING NON LIFE THREATENING � Intrapartum stillbirth � Apgar score 4-6 at 5 � Neonatal Death minutes � Apgar score <3 at 5 � O2 >24 hours minutes � Observation nursery � Admission to NICU � Birth trauma � Need for ventilation � HIE � IVH

33,812 1 or 2 prev CS 1 = 29,440 2 = 4,366 No prior vag delivery 28,406 Prior vag delivery 5,406 3,726 (68.9%)planned vag birth 7,614 (26.8%) planned vag birth 4,726 (62.6%) vag 3,297 (88.5%) vag

90 80 70 60 50 40 % 30 20 10 0 A B C D E F G H J K L M N P Hospitals with >1000 deliveries in BC, 2007-11, PSBC

Percent of women who attempted vaginal birth after Cesarean (VBAC) by LHIN of Birth Fiscal 14/15 90% 80% 70% 60% 50% Attempted VBAC 40% 30% VBAC not attempted 20% 10% 0%

Percent of women who attempted vaginal birth after Cesarean (VBAC) by Level of Care (LOC) Fiscal 14/15 90% 80% 70% 60% 50% Hospital (level of care 1) Hospital (level of care 2) 40% Hospital (level of care 3) 30% 20% 10% 0% Attempted VBAC VBAC not attempted

Percent of women who had successful VBAC among those who attempted VBAC by LHIN of Birth Fiscal 14/15 90% 80% 70% 60% 50% 40% Yes No 30% 20% 10% 0%

VBAC attempted VBAC successful % % n = 250 25.2 68.2 n = 346 43.9 71.0 n = 571 26.4 80.7 n = 363 36.0 70.9 n = 2,114 31.5 62.4 57.6 58.8 n = 59

There were no maternal deaths . � Composite risk of > 1 life � threatening outcome: No previous vag > 1 previous vag Pl vag Pl CS RR Pl vag Pl CS RR 165 (2.2) 179 (0.9) 2.52 (2.04-3.11) 73 (2.0) 16 (0.9) 2.06 (1.20-3.52)

Surgical intervention to control bleeding: significantly for women planning vaginal birth without a prior vaginal delivery (RR � 5.40, 95% CI 3.78–7.72) and with a prior vaginal delivery � (RR 7.67, 95% CI 2.40–24.52). Blood transfusion: significantly only for women planning a vaginal � birth without a prior vaginal delivery (RR � 1.44, 95% CI 1.01–1.72).

Uterine rupture: significantly only for women � planning a vaginal birth without a prior vaginal delivery (RR 6.93, 95% CI 3.65–13.16). Uterine dehiscence: significantly only for women � planning a vaginal birth without a prior vaginal delivery Source: “ Self Portrait ” by Amanda Greavette (RR 2.94, 95% CI 2.04–4.17).

� Composite risk of > 1 non-life threatening outcome: No previous vag > 1 previous vag Pl vag Pl CS RR Pl vag Pl CS RR 159 (2.1) 439 (2.1) 0.99 (0.82-1.18) 45 (1.2) 40 (2.4) Source: “ Andrea ” by Amanda Greavette 0.51(0.33-0.77)

� Composite risk of intrapartum stillbirth, neonatal death, or > 1 life threatening neonatal outcome: significantly elevated only for women planning a vaginal birth without a prior vaginal delivery No previous vag > 1 previous vag Pl vag Pl CS RR Pl vag Pl CS RR 61 (0.8) 100 (0.5) 1.65 (1.20-2.26) 14 (0.4) 11 (0.7) 0.57(0.25-1.26)

5 minute Apgar < 3 : significantly only for women � planning a vaginal birth without a prior vaginal delivery (RR 8.85, 95% CI 2.89–27.14). Admission to a neonatal intensive care unit : significantly only for women � planning a vaginal birth without a prior vaginal delivery (RR 1.54, 95% CI 1.04–2.26). Source: “ Sleep ” by Amanda Greavette

Composite risk of > 1 non-life threatening outcome: significantly for women planning a vaginal birth with a prior vaginal delivery (RR 0.67, 95% CI 0.52–0.86). No previous vag > 1 previous vag Pl vag Pl CS RR Pl vag Pl CS RR 333 (4.5) 887 (4.4) 1.02 (0.90-1.16) 143 (3.9) 96 (5.9) 0.67 (0.52-0.86)

87.1% of women in our sample � had only one previous cesarean birth. The direction and size of � differences for each outcome group according to planned mode of delivery was similar to those for the entire sample.

� The association between planned mode of delivery and adverse outcomes after 1-2 previous cesarean births may be modified by history of prior vaginal birth.

� Retrospective data. � Observational study design. � Use of composite outcomes. � Smaller sample size of women with a prior vaginal delivery. � No data on inter-pregnancy interval or ethnicity.

Overall, risks for adverse � outcomes after 1-2 previous cesarean births are reduced among women with a prior vaginal birth compared to without a prior vaginal birth. Absolute differences between � planned vaginal birth compared with planned cesarean birth remain small. Our data offer women and their � caregivers the opportunity to consider risk profiles separately for women who have and have not had a prior vaginal delivery.

BORN CONFERENCE 2017 April 24 & 25, 2017 Unlocking the Value of Data Marriott Eaton Centre Toronto BORN is hosting a two-day conference to bring clinical care providers, students, researchers and decision makers together to share experiences, enhance knowledge, foster partnerships, and promote research. www.BORNOntario.ca A provincial program of CHEO