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Background, Indications, Risks

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:​
  1. Overall reduction c-section rate​
  2. Reduced length of hospital stay​
  3. 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:

  1. 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:

MaternalFetalOther
Uterine anomaly​*Preeclampsia/HTN
​Ruptured membranes​
APH​
*Abruption history​Active labour
​Cardiac disease
​Obesity​
ECG abnormalities
​Abnormal pelvis​
Age >45​
Allergies​
History of cesarean delivery​Diabetes
​Dilated cervix​
Grand multipara​Hyperthyroidism
​Irregular T4​
Growth restriction​*Abnormal cardiotocography​
Fetal anomaly
​Macrosomia​
Hyperextension of head
​Unstable lie​
*Doppler abnormalities
​Fetal distress​
Positive non-stress test​
Rhesus immunization​Uteroplacental transfusion​
Oligohydramnios​
Restrictive nuchal cord​Inexperienced obstetrician​Anterior placenta​
Polyhydramnios​
Single umbilical artery​
Source: ROSMAN et. al. (2013), Contraindications for external cephalic version in breech position at term: a systematic review. Acta Obstetricia et Gynecologica Scandinavica, 92: 137-142. https://doi.org/10.1111/aogs.12011

*Level III evidence for the following contraindications:

  1. Maternal history or sign of abruption​
  2. Maternal severe preeclampsia or HELLP​
  3. 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

  1. Transient fetal heart rate changes – 4.7%. Usually stabilizes after termination of procedure.
  2. 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

Alternatives to ECV

2.1.7 Summary

2.1.8 References

Updated on October 28, 2021

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