Breech presentation occurs in 3–4% of all term pregnancies.1 Since the publication of the results of the Term Breech Trial in 2000,2 the cesarean delivery rate in women with a fetus in the breech presentation has increased substantially in most developed countries. The primary objective of the external cephalic version is to improve the chances of having a successful vaginal cephalic delivery. A meta-analysis of five randomized controlled trials that were conducted to evaluate the pregnancy outcomes of external cephalic version demonstrated that external cephalic version attempts at or near term are associated with a significant reduction in noncephalic births and cesarean delivery rates.3 The recommended current guidelines describe external cephalic version as an effective obstetric technique that reduces the cesarean delivery rate for malpresentation and should therefore be offered to women presenting with singleton breech fetuses at term.4–8
Although it is clear that external cephalic version reduces the incidence of cesarean delivery for women with breech presentation,3 there is some controversy regarding whether the risk of cesarean delivery is equivalent for women with spontaneous cephalic presentation. Several studies that were conducted to estimate pregnancy outcome after successful external cephalic version reported a cesarean delivery rate of 8–30%. Several studies have compared the cesarean delivery rate after successful external cephalic version with spontaneous cephalic-presenting pregnancies; two studies reported a low cesarean delivery rate after successful external cephalic version,9,10 three studies reported no significant difference,11–13 and eight studies demonstrated an increased risk for cesarean delivery after successful external cephalic version.14–22 A meta-analysis of six studies concluded that after successful external cephalic version, women had a more than twofold increased probability of cesarean delivery compared with women with spontaneous cephalic presentation (relative risk, 2.04; 95% confidence interval [CI] 1.43–2.91). The increased rate of cesarean delivery was explained by increased intrapartum dystocia and suspected fetal distress.23
When considering an external cephalic version attempt compared with elective cesarean delivery, the increased risk of intrapartum cesarean delivery may influence the decision. Thus, women may prefer to undergo a safe elective cesarean delivery rather than a more precarious external cephalic version. Understanding the reasons and risk factors for the increased cesarean delivery rate in this group will allow physicians to perform proper patient selection and intrapartum management to maximize the chances for successful vaginal cephalic delivery. Therefore, the main objective of the current study was to estimate the association between timing of delivery after successful external cephalic version at term and the risk for cesarean delivery.
MATERIALS AND METHODS
This retrospective cohort study was conducted in the maternal-fetal unit of a tertiary center university teaching hospital with approximately 5,000 deliveries per year. The study population consisted of all of the women who had a successful external cephalic version performed in our center between January 1997 and January 2010.
During the study period, in the absence of contraindications, all of the women with singleton pregnancies with confirmed breech presentation at or after 37 weeks of gestation were offered an external cephalic version. All of the patients gave informed consent.
Absolute contraindications for external cephalic version included any absolute indications for cesarean delivery (eg, placenta previa), significant fetal or uterine malformation, nonreassuring fetal heart rate pattern, ruptured membranes, placental abruption, and active labor. Relative contraindications included previous cesarean delivery, maternal obesity (body mass index [calculated as weight (kg)/[height (m)]2] greater than 27), intrauterine growth restriction, oligohydramnios (amniotic fluid index less than 7 cm), and substantial polyhydramnios (amniotic fluid index greater than 25 cm). Women were not eligible for external cephalic version in the presence of two or more relative contraindications.
An ultrasound scan was performed before the procedure to verify the fetal and placental position, biophysical score, and estimation of fetal weight. In addition, fetal monitor tracing was obtained to confirm fetal well-being before the external cephalic version and after the procedure.
All of the external cephalic versions were performed in the delivery room by an experienced senior obstetrician with the aid of ultrasonography. Tocolysis by 50 mg intravenous ritodrine (until April 2003) or 20 mg oral nifedipine (from May 2003) was administered 20 minutes before the procedure unless the patient had a contraindication for these medications. After the external cephalic version procedure (successful or unsuccessful) and recording of a reactive cardiotocogram, the patient was discharged for routine obstetric care until the onset of spontaneous labor. According to our policy, we do not perform “stabilizing induction” for successful external cephalic version.
Clinical data for this study, including maternal demographics, obstetric parameters, external cephalic version details, and delivery outcomes, were collected during each external cephalic version attempt as part of routine documentation in our institution (data were obtained from the patient, the ultrasound examination, and the senior obstetrician performing the external cephalic version). To assess the relationship between the interval of time from external cephalic version to delivery and the risk for cesarean delivery, we compared the mode of delivery (vaginal delivery compared with cesarean delivery) and the time from external cephalic version to delivery using the Pearson χ2 test. In addition, clinical characteristics were compared between women who underwent vaginal delivery or cesarean delivery. For statistical comparisons between the groups, we compared gravidity, parity, body mass index, prior cesarean delivery, prior breech, placental location, amniotic fluid index, type of breech, ultrasound and clinical estimation of fetal weight, time between external cephalic version and delivery, Apgar score, and birth weight using a univariable model followed by multiple logistic regression analysis.
Stepwise logistic regression was applied, and the variables that were significantly associated with mode of delivery in the univariable approach were included in the model. The odds ratio (OR) of each variable was calculated with a 95% CI. P<.05 was considered to be statistically significant. The Statistical Package for Social Sciences for Windows 17 was used for statistical analysis of all data. The study was approved by the Hadassah Medical Organization institutional review board on July 9, 2010.
There were 909 external cephalic version attempts during the study period. The success rate was 76.1% and 49.6% for multiparous and nulliparous women, respectively; the overall successful rate was 64%. Of 585 successful external cephalic versions, 502 had complete follow-up data and therefore were available for this analysis. Of the 502 women included in this study, 51 women (10%) required intrapartum cesarean delivery, whereas 451 women (90%) had a vaginal delivery (Fig. 1).
There was no significant difference between the groups in terms of body mass index, prior cesarean delivery or prior breech status, placental location, amniotic fluid index, type of breech, ultrasound or clinical estimation of fetal weight, or Apgar score. The only between-group difference in background factors was a higher rate of primiparous women in the cesarean delivery group (46.9% compared with 30.3%). The cesarean delivery rate was 14.6% and 7.7% for primiparous and multiparous women, respectively (P=.018, χ2 test) (Table 1).
Data regarding the time interval between external cephalic version and delivery data were available for 483 women who had a successful version, representing 53.1% of fall external cephalic version attempts; 139 women (29%) gave birth less than 96 hours from external cephalic version, whereas 344 women (71%) gave birth more than 96 hours from external cephalic version. The interval from external cephalic version to delivery was ranged from a few hours to 34 days. The incidence of cesarean delivery was 16.5% and 7.8% in women who gave birth before and after 96 hours from the time of the external cephalic version, respectively (P=.004, χ2 test). The OR for intrapartum cesarean delivery for each of the first 4 days from external cephalic version ranged between 2.21 and 3.11 and was statistically significant for primiparous as well for multiparous women. The OR for cesarean delivery when delivery occurred less than 96 hours from external cephalic version was 2.97 and 2.27 for nulliparous and multiparous women, respectively (Table 2). There was no significant difference in cesarean delivery risk between the groups 5 days after external cephalic version.
In a multiple logistic regression analysis, the adjusted OR for cesarean delivery among primiparous women was 2.135 (P=.016, 95% CI 1.15–3.96) and the adjusted OR for cesarean delivery in women who gave birth within 96 hours of the time of external cephalic version was 2.541 (95% CI 1.36–4.72) (Table 3).
The reconversion rate in our series was 0.8% (four cases out of 503 successful external cephalic versions). All cases of reconversion were included in the study and were classified as successful external cephalic versions, eventually those women had cesarean delivery resulting from breech presentation.
Our study demonstrated that intrapartum cesarean delivery was more likely to be performed if delivery occurred within the first 4 days after the external cephalic version. Moreover, delivery within 96 hours after the external cephalic version carried a more than twofold increased risk for cesarean delivery for both nulliparous and multiparous women. In an earlier study that was conducted to evaluate predictors of successful vaginal delivery in women undergoing external cephalic version at term, the timing of delivery after successful version was not examined.24 Several studies have reported an increase in the cesarean delivery rate after successful version; this increase is generally attributed to dystocia and intrapartum fetal distress.16–18,21–23 Although several hypotheses have been suggested, the reasons for the increased cesarean delivery rate in women with successful external cephalic version remain unclear. Previous studies have reported a genuine biologic difference between breech fetuses and cephalic-presenting fetuses such as smaller head circumference, lower birth weight, and lower fetoplacental ratio.25–27 Thus, breech-presenting fetuses might be less tolerant to stress during labor, which results in a higher risk for intrapartum cesarean delivery resulting from fetal distress. It seems that this condition is often not reversed by a successful external cephalic version, which changes only the presentation. Another hypothesis relates to uterine malformations or pelvic anomalies that predispose the fetus to breech presentation and can also lead to higher risk for dystocia during labor.28 Another hypothesis is related to latent adverse effects associated with external cephalic version (eg, fetomaternal hemorrhage and placental abruption) that may cause a reduction in the ability of the fetus to tolerate a successful vaginal delivery. The last hypothesis suggests that after an external cephalic version, the fetal head may remain unmolded, unengaged, or in an asynclitic position, precluding vaginal delivery and increasing dystocia. The present study supports and provides a possible explanation for the last hypothesis in which a certain interval of time may be required for the fetal head to achieve adequate engagement before the initiation of labor.
In our study, we found that the two parameters associated with increased risk for cesarean delivery were delivery less than 96 hours after external cephalic version and primiparity. Although several previous studies investigated the time interval between external cephalic version and delivery, none of them demonstrated an association with an increased rate of cesarean delivery.9,11,16,18 Furthermore, like we found in the current study, other studies reported an increased likelihood of cesarean delivery after successful external cephalic version among primiparous women.16,17,19 However, in contrast to the results of several previous studies, we did not find any association between previous cesarean delivery or birth weight and an increased cesarean delivery rate.
A limitation of this study was the retrospective collection of the data gathered from women who underwent successful external cephalic version. Therefore, future prospective studies that compare the risk for cesarean delivery after successful external cephalic version and spontaneous cephalic presentation are required to validate our results.
After successful external cephalic version, some physicians perform a “stabilizing induction” (ie, amniotomy and induction of labor) to avoid reversion to breech). The latest guidelines of both the American College of Obstetricians and Gynecologists and the British Royal College of Obstetricians and Gynaecologists do not recommend immediate induction (stabilizing induction) after external cephalic version in the absence of valid indications as a result of a significant intrapartum complication rate (level of evidence III).4,29 As demonstrated in this study, delivery before 96 hours from external cephalic version may be associated with an increased risk of cesarean delivery; therefore, stabilizing induction should perhaps also be discouraged. Our results support the American College of Obstetricians and Gynecologists and British Royal College of Obstetricians and Gynaecologists recommendations.
In conclusion, accurate knowledge of the risk factors for cesarean delivery after successful external cephalic version will assist physicians in evaluating the likelihood of successful vaginal delivery postversion, thus improving patient counseling before this procedure.
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