Evidence Based External Cephalic Version || Module by Dr. Angel Shan
Learning Objectives
- Review a standard protocol for performing an ECV
- Examine the patient factors that help to predict a successful ECV
- Discuss the procedural variables that improve the rate of success
Background Information
- 3-4% of term pregnancies are in breech presentation.
- External cephalic version is physical manipulation of a non-cephalic presenting fetus through the abdominal wall to achieve a cephalic presentation.
- Successful ECV has been shown to have:
- Overall reduction c-section rate
- Reduced length of hospital stay
- Lower risk of developing endometritis and sepsis
Success Rates of ECV
Conclusion: Average success rate approximately 49-58% with lower rates in nulliparous women.
2008 Meta-analysis in Obstetrics & Gynecology looking at 84 studies:
- Successful version rates ranged from 16-100%
- Overall pooled success rate was 58%
2019 large cohort study in BJOG with 2614 women undergoing ECV
- Overall success 49%, 95% CI 47.0-50.9%
- 40% nulliparous women
- 64% in others
- 97.3% cephalic at birth
Positive Predictive Factors
Summary of Positive Predictive Factors of ECV Success:
- Parity
- Ultrasound measured size of amniotic fluid preceding the fetal part (fore-bag)
- Transverse or oblique lie
Evidence
- Single-centre retrospective study including all candidates for ECV between 36-41 weeks GA
- Variables: BMI, AFI, GA, parity, location of placenta, fetal trunk posture, time in breech presentation before the procedure, and ultrasound measured size of amniotic fluid preceding the fetal part (fore-bag)
Results
- Patients with BMI >29 had lower probability of success regardless of fore-bag size
- Version outcome in BMI <29 was associated with fore-bag size
- Fore-bag size >1 cm had higher success rate
- Fore-bag size <1cm in nulliparous women resulted in lower success than multiparous women
- One-unit increase in BMI resulted in reduced odds of success (OR 0.6)
- Number of previous deliveries increased odds (OR 6)
Negative Predictive Factors
- Nulliparity
- Advanced dilation
- Fetal weight <2500 g
- Anterior placenta
- Low station/descent of breech into pelvis
Controversial Factors
- Normal or increased amniotic fluid volume
- Location of placenta
- Maternal weight
- Early labour
Impact of Provider Experience on Success
Introduction of a dedicated team increases the success rate of external cephalic version: A prospective cohort study (Thissen et.al., 2019)
- Prospective cohort study, N=673 women with singleton breech fetus comparing ECV success rate prior to and after a dedicated team
- Dedicated team of 6 gynecologists and 6 midwives
- Standard information for patients (leaflet, movie, ECV checklist with informed consent and risks)
- Absolute contraindications: mutiples, labour, indication for planned C/S, abnormal umbilical Dopplers, Rh immunization, vaginal bleeding <7 days prior, placental previa, ruptured membranes, suboptimal FHR, congenital uterine abnormalities
Results:
- ECV Success rate increased from 39.8% to 69.5% (p<0.001)
- Greatest increase was seen in nulliparous women from 23.5% to 58.5%, P=0.002
- Found an increase in vaginal delivery rate and decrease in c-section rate
Conclusion:
ECV performance by a dedicated team, consisting of experienced providers increases ECV success rate.
Impact of Timing of ECV on Success – Is Earlier Better?
Unblinded multi-centre RCT
N=1534 with singleton breech fetus
Randomized to:
1) Early ECV at 34+0 to 35+6 weeks GA (n=767)
2) Delayed ECV at >37+0 weeks GA (n=774)
Primary outcome: rate of c-section
Secondary outcome: rate of preterm birth
Results
Early ECV resulted in fewer fetuses in non-cephalic presentation (RR 0.84, 95% CI 0.75-0.94) with no difference in rates of c-section (52% vs 56%, RR 0.93, CI 0.85-1.05) or risk of preterm birth (6.5% vs 4.4%, RR 1.48, 95% CI 0.97-2.26)
Conclusion
Early ECV increases the likelihood of cephalic presentation at birth with no decrease in c-section rate or increase in preterm birth risk.
Impact of BMI on Rates of Successful ECV in Those with Prior Cesarean Section
- Cross-sectional study looking at 2329 women who underwent ECV after one previous c-section.
Conclusions:
- No correlation of BMI with the rate of successful ECV along women with one prior c- section.
- Risks of adverse maternal and neonatal outcomes were similar.
Impact of Persistent Breech Presentation on Rates of Successful ECV
- Persistent breech presentation defined as persistent breech presentation during all ultrasound examinations performed between the anatomy scan and the gestational week when ECV was attempted
- N=684 women underwent ECV attempt
- Overall success rate of 61.5%
- Persistent breech success rate: 19.6%
- Not persistent breech success rate: 82.0%
Indications and Contraindications
Indications:
All women with a breech pregnancy at or near term should be offered an ECV if there are no contraindications. And if:
- Ultrasound confirmation of:
- Non-vertex presentation
- Normal amniotic fluid
- Exclusion of fetal anomalies
- Placental location
2. Reassuring NST or biophysical profile prior to the procedure.
3. Absence of contraindications.
Absolute Contraindications:
Vaginal delivery is contraindicated (Placenta previa, not a candidate for VBAC, etc.)
Relative Contraindications:
There are maternal, fetal and placental factors:
| Maternal | Fetal | Other |
| Uterine anomaly*Preeclampsia/HTN Ruptured membranes APH *Abruption historyActive labour Cardiac disease Obesity ECG abnormalities Abnormal pelvis Age >45 Allergies History of cesarean deliveryDiabetes Dilated cervix Grand multiparaHyperthyroidism Irregular T4 | Growth restriction*Abnormal cardiotocography Fetal anomaly Macrosomia Hyperextension of head Unstable lie *Doppler abnormalities Fetal distress Positive non-stress test Rhesus immunizationUteroplacental transfusion | Oligohydramnios Restrictive nuchal cordInexperienced obstetricianAnterior placenta Polyhydramnios Single umbilical artery |
*Level III evidence for the following contraindications:
- Maternal history or sign of abruption
- Maternal severe preeclampsia or HELLP
- Fetal distress (abnormal cardiotocography or abnormal Doppler flow)
Is ECV safe in those with previous Cesarean Section?
Cesarean Section is not a contraindication for ECV.
Evidence
- 6 cohort studies and 2 case-control studies with N = 14515
- Overall success found to be between 63-81%, similar to those without a previous c-section
- Vaginal delivery rate lower than those without a previous c-section (OR 0.26)
- No cases of uterine rupture during ECV were reported in women with a previous c-section
Conclusion:
Prior low transverse c-section is not a contraindication to ECV.
Risks of ECV
- Transient fetal heart rate changes – 4.7%. Usually stabilizes after termination of procedure.
- Overall rate of adverse events after ECV is <1%. Possible adverse events include:
- Placental abruption
- Fetomaternal hemorrhage
- Rupture of membranes
- Umbilical cord prolapse
- Stillbirth
Next Module
Standard Protocol for Performing an ECV