Preoperative predictors of successful External Cephalic Version with breech presentation at term: a single centre experience

doi:10.21203/rs.3.rs-3233793/v1

Objective

To determine the factors associated with the external cephalic version (ECV) and evaluate the success rate ECV of at term in China.

Methods

207 consecutive patients who attempted ECV with a breech presentation at term were included from January 2017 to January 2023. Patients with a successful ECV were divided into the ECV success group. Patients who performed ECV but had a repeat breech presentation were divided into the ECV failure group. The factors for ECV success was carried out by multiple logistic regression analyses.

Results

The success rate of ECV was 68.6%(142/207) among 207 pregnancies with breech presentation at term. The reasons for failed ECV were not turning at all after four to five attempts(38/65, 58.5%), followed by fetal distress(7/65, 10.8%). Three predictive factors were identified and associated with a successful ECV: larger AFI, the use of tubutaline and lower HC/FL ratio.

Conclusions

This ECV prediction model based on a Chinese population to predict the success of ECV that is easy to use and incorporates a limited number of objective patient characteristics. The level of AFI, use of tubutaline, and ratio of HC/FL are independent determinants of the final presentation.

external cephalic version

breech presentation

risk factor

prediction model

The incidence of non-cephalic presentation in full-term pregnancies is 3–4%^[1]. Breech is an indication for cesarian section Since breech deliveries company with higher risk of fetal asphyxia and intrauterine accidents^[2]. In China, the rate of cesarean delivery with the non-cephalic presentation is estimated to be 90%^[3]. Although cesarean section(CS) is relatively safe, but more and more patients were afraid of the CS and attempt the procedure external cephalic version (ECV). ECV is an operation which was given a pressure to a woman’s abdomen and turnover the fetus in either a forward or backward roll to finish a vertex presentation^[4]. Once ECV is successful, the chances for a vaginal delivery increase.

External version was performed since 2012 in our unit. At the beginning, only fewer patients attempted this procedure. With the delivery desires, patients always counsel about the risks factors and success rates of version. There are too many factors with ECV success in different multiple studies^[5–6]. Success rates for ECV also ranged from 35 to 86%, which was big span^[7]. Patient counseling and decision making were all based on others’ reports. In order to provided unbiased non-directive information in China, Success rate of ECV and develop prediction models for the chance of successful ECV for breech presentation at term were evaluated.

2.1 Patient identification

The Ethics Committee of Ningbo Women and Children’s Hospital (approval number: EC2030-050) approved our retrospective study, which was conducted in accordance with the Declaration of Helsink. We had the written informed consent from all the participants.

We extracted information about the maternal history and clinical outcomes of delivery from medical and surgical records. This study was included all women who attempted ECV between January 2017 to January 2023 were included in the study.

The inclusion criteria included: (a) singleton pregnancy; (b) a noncephalic presentation at 37–38 weeks gestation and scheduled for ECV.

The exclusion criteria included: (a) cesarean delivery (CD) cannot be avoided, diagnosed with placenta previa or twin pregnancy; (b) contraindications were early labor, oligohydramnios or rupture of membranes, severe fetal growth restriction, uterine malformation, prior abruption and prior cesarean delivery; (c) incomplete history and surgery records were available; and participants requested repeat CD during delivery.

Figure 1 showed the flowchart of this study.

2.2 Data collection

Based on factors that were previously linked to ECV in other studies and data availability in our current clinical database^[8–10], the demographic variables included maternal age, parity, body mass index (BMI) in admission for ECV, gestational age at ECV, estimated birth weight(EFW), amniotic fluid index(AFI), fetal position, placental location (anterior, posterior), number of loops of uchal cord, fetal growth parameters: head circumference(HC), femur length(FL), HC-to-FL(HC/FL) ratio. EFW was calculated with the Hadlock formula. HC-to-FL ratio was the ratio of head circumference to femur.

The successful ECV was defined as cephalic presentation 30 minutes after the procedure, confirmed by ultrasonography, and cephalic presentation at delivery. The primary outcome was successful ECV and the second outcomes were the maternal and neonatal outcomes included emergency CD, NICU admission, Apgar score (5 min, ≤ 7).

2.3 Procedure

Before the procedure of ECV, consent for procedure, fasting for 6 hours, and non-cephalic presentation checked by ultrasound were all done. Participants who were informed of the benefits and disadvantages of ECV under NA, and agreed the anaesthesia, unless the patients refused the NA. But the general anesthesia must be performed if there was an emergency cesarean delivery would be preformed immediately.

During the procedure of ECV, it was preformed by the same experienced operators (Dr. Ying or Dr. Chen) who had been working for 20 years in OR which had the facilities for emergency cesarean delivery, ultrasound for the real-time guidance, and fetal heart rate monitor. Firstly, all participants were open intravenous access. After injection of 0.25 mg subcutaneous terbutaline and NA was done, Each obstetrician made no more than five ECV attempts. When the fetal heart rate or the real-time ultrasound guidance found fetal distress or Fetal heart slowing due to placental abruption, the emergency cesarean delivery would be preformed immediately.

After the procedure, regardless of the success of the operation, we had to do continuous electronic fetal heart rate monitoring for the patients to assess the fetal heart rate at least for 30 min to 2 hours and do an ultrasound to check the fetal presentation. Anti-D immunoglobulin was given for rare blood type. In the absence of any indication for admission, the women were advised routine antenatal care until delivery.

2.4 Statistical analysis

The Mann-Whitney U test was used to examine continuous variables, and Fisher’s exact test or chi-squared test was used to examine categorical variables. Continuous variables were presented as means ± SD and categorical variables as median and interquartile range(IQR). All continuous predictors were assumed to be linearly associated with the outcome. Multiple logistic regression analyses were performed to identify the factors for ECV failure. All statistical analyses were performed using SAS version 9.3 (SAS Institute, Inc., Cary, NC). Statistical significance was defined as P < 0.05.

Between 2017 and 2023, 261 cases were included. Fifty-four participants who received repeat CD at their own or their family's request were excluded. Of the remaining 207 women participants were performed ECV, while 142 women had a successful ECV, while 65 had a repeated CD. The rate of successful ECV in our study was 68.6% (Fig.1).

Reasons for failed ECV

The reasons for failed ECV were not turning at all after four to five attempts(38, 58.5%), followed by fetal distress(7, 10.8%), Placental abruption(6, 9.23%), still breech presentation with ECV(6, 9.23%) and Cord prolapse(1, 1.54%). (Fig.2)(Table 1)

Table 1. Reasons for failed ECV

reasons	Total(n=65)	%
Not turning	38	58.5
Fetal distress	7	10.8
Placental abruption	6	9.23
Still breech presentation	3	4.62
Cord prolapse	1	1.54

Data in the table are presented as n (%), mean±SD, and median [interquartile range]. NICU: neonatal intensive care unit.

Predictors of successful ECV

The clinical data of all participants are shown in Table 2. The HC/FL ratio were significantly higher in the ECV failure group than in the ECV success group (P=0.018). The amniotic fluid index and the use of tocolytic were significantly lower in the TOLAC failure group than in the TOLAC success group (P < 0.001). No significant differences in age, body mass index at ECV, parity, gestational weeks , placental implantation, Loops of nuchal cord, neuraxial anesthesia and EFW during ECV were observed between the ECV success and ECV failure groups.

Table 2. Demographic and clinical characteristics of the patients underwent ECV.

Clinical parameters	Successful group (n=142)	Failed group (n=65)	P value
Maternal age (years),	31.12±4.09	30.58±3.97	0.379
BMI at ECV(kg/m2),	25.83±3.07	26.04±3.27	0.660
Parity, n (%)			0.394
Nulliparous	63(44.4%)	33(50.8%)
Multiparity	79(55.6%)	32(49.2%)
Gestational weeks during ECV, (weeks)	37.90±0.90	37.83±0.69	0.581
EFM during ECV (kg)	3.09 ±0.31	3.06±0.34	0.412
HC/FL ratio	4.79±0.24	4.88±0.19	0.015*
placental implantation, n (%)			0.687
Anterior	55(38.7%)	23(38.5%)
Posterior	74(52.1%)	29(46.2%)
Lateral or Fundal	13(9.2%)	10(15.4%)
AFI (cm)	12.5±3.5	11.0±3.1	0.006*
Loops of nuchal cord (yes), n (%)	57(40.1%)	22(33.8%)	0.389
Use of tocolytic, (yes) n (%)	126(88.7%)	45(73.8%)	0.006*
Neuraxial anesthesia, (yes) n (%)	33(23.2%)	19(29.2%)	0.359

Data in the table are presented as n (%), mean±SD, and median [interquartile range].

BMI: body mass index; EFW: estimated fetal weight; AFI: amniotic fluid index.

Multiple logistic regression analysis showed that the level of AFI (OR = 1.107, 95% CI: 1.006-1.029, P = 0.027) and the use of tubutaline were positively associated with success ECV(OR = 2.612, 95% CI: 1.183-5.769, p=0.0175) . In contrast, the HC/FL ratio (OR = 0.097, 95% CI: 0.017-0.551, p=0.0084) was negatively related to success ECV. (Table 3).

Table 3. Multiple regression logistic of characteristics affecting the outcome of successful ECV.

	OR	95% CI	P
AFI (12.3cm)	1.107	1.006-1.029	0.0027
The use of Tubutaline(yes)	2.612	1.183-5.769	0.0175
HC/FL ratio( 4.838)	0.097	0.017-0.551	0.0084

OR, odds ratio; CI, confidence interval.

We described a retrospective study to identifying the factors associated with successful ECV attempts and developing a prediction model to identify patients with lower likelihood of success. The success rate of ECV was 68.6% in our study and the level of AFI, use of tubutaline, and ratio of HC/FL are independent determinants of the final presentation, whereas other variables had no statistically significant effect on the success rate.

The most reasons for failed ECV was not turning at all after four to five attempts by two single experienced physicians. There were 38 fetus not turning at all and with a well fetal heart rate. For these groups, we can try a second ECV under NA. Although at the beginning we used anesthesia to facilitate ECV in the current study, the anesthesia and abnormal bleeding, hypotension were still worth discussing. Emergency CD is a serious complication during or after the procedure of ECV^[11]. The incidence of emergency CD in our present study was 6.25% (13/207), Compared and contrasted with other studies reported that the rate of emergency CD during ECV was 1.0 to 4.2%^[12–13]. The most reasons was fetal distress during the the procedure of ECV^[14]. It is noteworthy that one case of cord prolapse occurred in a woman with successful ECV after 8 hours later, suggesting that maximum attention should be paid in cases of premature rupture of membrane.

The level of amniotic fluid index was a positive factor associated with successful ECV in the present study by multiple logistic regression analysis, meanwhile the univariate analysis revealed that the level of amniotic fluid index was significantly higher in the TOLAC success group than in the TOLAC failure group. Cohort studies conducted in Germany and Australia also showed that AFI was independently associated with failed ECV^[15–16]. Optimum cut value is 12.3cm(Table 3). One of the strengths in our study was women with AFI below 8 cm were all included (14/207), although some studies refused to perform ECV in patients with the AFI below 8 cm^[17]. Some surgeons have decided on a threshold of AFI below 10 as a reasonable cutoff^[18]. There are 6 patients with successful ECV with the AFI ranged from 5-8cm and 8 patients with failed ECV with the AFI ranged from 5-8cm. So a future replicate study on multi-center with the AFI ranged from 5-8cm is warranted.

In this study, the HC/FL ratio was negatively related to successful ECV, meaning that if the ratio is lower, the opportunity for successful TOLAC is higher. The objective ratio can easily obtained from the patient characteristics, which have the similar results in Carly’ s study^[19]. The ratio can can improve parameter measurement, and reduce measurement error from different ultrasound physicians. However, other studies have found different results, that the BPD or HC was unrelated to the success of ECV^[20–21]. A possible reason for this difference is that the accuracy of B-ultrasound in evaluating the longth of BPD or HC is still controversial^[22–23]. According to our study, pregnant women with a higher ratio of HC/FL may be not suitable for ECV and can choose cesarean delivery (CD).

The use of Tubutaline was also a positive factor with the ECV(OR = 2.612) by multiple logistic regression analysis, similar with Fernandez’s randomized study of terbutaline^[24]. More and more Studies supports the use of parenteral tocolysis to improve the success of ECV while Data were insufficient to analyze adverse effects of b-stimulant tocolysis^{[2, 25]}. In view of the insufficient data for the use of agent, we need a high RCT.

The large sample size and its development in a contemporary population were the strengths of this study. The variables were were all objective, easily obtained, and clearly defined variables, compared with factors that use more subjective markers such as possibility of palpation of the fetal head. Our principles are if women attempted ECV, we will do it, even though the AFI was below 5cm. At the initial implementation of this procedure, uterine tocolysis or neuraxial analgesia were often employed. As technology advances and emergency caesarean delivery are perfected well, Only uterine tocolysis were often employed.

Well, we also found several limitations to this study. First, with regard to patients with ECV failure, it is noteworthy that no second ECV was found. Some studies was performed the second ECV for the failed. Second, This study was only conducted at a single center, and thus further randomized, controlled trials and multicenter studies are required in the future. Finally, based on individuals at a single site, Further studies in other populations are required to confirm our findings.

Our study adds to the limited evidence that External cephalic version is effective in increasing the rate of vaginal births and decreasing the incidence of cesarean delivery with breech presentation. This ECV prediction model based on a Chinese population to predict the success of ECV that is easy to use and incorporates a limited number of objective patient characteristics. But our findings need to be confirmed in larger samples with patients of different institutions.

Ethics approval and consent to participate: This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethnic Committee of the Ningbo Women and Children’s Hospital (approval number: EC2030-050). All of the participants provided written informed consent. All data were collected from the electronic medical record system in the department of Obstetrics Medicine Center. Data were anonymized and de-identified before analysis.

Consent for publication Not applicable.

Availability of data and materials: The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests: The authors declare no conflict of interest.

Funding: This study was supported by Medical Science and Technology Project of Zhejiang Province, China (2021KY1057) and funded by the project of NINGBO Leading Medical & Health Discipline (2010-S04).

Authors' contributions: ZRD and AEC: Data Collection, Manuscript Writing and Data Analysis; XXL: Data Collection, XBH: Project Development, Manuscript Editing. All the authors reviewed and approved the final version of the manuscript.

Acknowledgements: We would like to express my gratitude to all those who helped me during the writing of this manuscript. Thanks to all the peer reviewers for their opinions and suggestions.

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No competing interests reported.

Preoperative predictors of successful External Cephalic Version with breech presentation at term: a single centre experience

Status:

Version 1

Abstract

Objective

Methods

Results

Conclusions

Figures

1 Background

2 Methods

2.1 Patient identification

2.2 Data collection

2.3 Procedure

2.4 Statistical analysis

3 Results

4 Discussion

5 Conclusions

Declarations

References

Additional Declarations

Status:

Version 1