Background: The Term Breech Trial has considerably increased the number of cesareans. External cephalic version (ECV) might be an effective method of lowering the rate of cesareans; its efficacy has been well established. However, although in the absence of anesthesia the risks are thought to be low, most studies have used populations too small to allow definite conclusions on version-related risks.

Methods: In an attempt to make an inventory of these risks, we have systematically analyzed 44 studies, covering a total of 7377 patients from 1990 to 2002. The studies used were derived from a Medline and Embase search.

Results: The most frequently reported complications were transient abnormal cardiotocography (CTG) patterns (5.7%). Persisting pathological CTG readings (0.37%) and vaginal bleeding occur rarely (0.47%). The incidence of placental abruption was even lower, at 0.12%. Fetomaternal transfusion was absent in five out of seven studies, with a mean incidence of 3.7%. Emergency cesareans were performed in 0.43% of all versions. Perinatal mortality was 0.16%.

Conclusions: External cephalic version seems to be a safe procedure.

Submitted 2 April, 2003; Accepted 26 June, 2003

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Introduction

In 2000 the results of the International Randomized Term Breech Trial were published (1). This study seemed to confirm the presumption that a primary cesarean section would reduce morbidity and mortality among children in breech presentation. Moreover, in the short term, complications in patients having had a cesarean were not more frequent than after vaginal delivery (2).

Up until then, the prevailing opinion was that with favorable factors present (normal fetal growth and pelvis, flexion of head and good progression of labor), a “trial of labor” was good practice. The Term Breech Trial, however, had a major impact on the attitude of obstetricians towards vaginal delivery (3). The number of cesarean sections for breech presentation had been rising slowly over the past decades, and has further increased considerably ever since. This development put breech presentation in third place as the most common reason for cesarean section and in some hospitals almost all children in breech are now delivered abdominally (4,5).

Increasing concerns have been expressed about the consequences of this large increase in the number of patients undergoing a cesarean section, which is in fact still a fairly major surgical intervention (6). Besides a rise in associated morbidity (and mortality), there will also be an important rise in the number of pregnancies with a scarred uterus, with all the related risks (7). In addition, with a progressively decreasing number of vaginal breech deliveries, this type of delivery will become a skill that young obstetricians in training will never adequately obtain (7,8). Finally, the impact on healthcare budgets must be taken into consideration (5).

The desire to prevent a strong rise in cesareans aroused new interest in methods to avoid breech presentation. The latest guidelines of both the American College of Obstetricians and Gynecologists (ACOG) and the British Royal College of Obstetricians and Gynaecologists (RCOG) recommend using external cephalic version (ECV) to lower the number of breech presentations (8,9). This renewed interest also revived questions regarding effectiveness and safety. Most of the recent version studies deal mainly with success rates, while safety issues remain unclear. To justify the use of ECV as an alternative to a primary cesarean more data are required regarding complications and their incidence. Therefore, following Zhang et al. (10), we have made an inventory of the complications in studies over the past decade. It seemed most obvious here to start from the period studied by Zhang (1980–91). Moreover – and also because of previous studies – the procedure and use of tocolysis seem to have gained more uniformity during the past decade compared with earlier times.

A Medline and Embase search was performed using the search terms “external,”“version” and “breech.” All studies published between January 1990 and December 2002 in English, German and Dutch were eligible. References in the papers studied were also screened for useful publications. Studies providing unclear or insufficient data were excluded. Further inclusion criteria were: healthy pregnant women with a singleton breech pregnancy, external version not earlier than 36 weeks of pregnancy, confirming a good fetal condition in advance by performing cardiotocography (CTG) registration, exclusion of evident fetal anomalies or pathology such as growth retardation seen in ultrasound examination, no use of anesthesia and no use of any pharmacological interventions other than tocolytic medication.

For each included study different sorts of complications and their incidence were analyzed. Complications were described as transient or persisting abnormalities in fetal heart rate registration during or after ECV, occurrence of vaginal blood loss, placental abruption or “other” complications. In the rare cases where complications were said to have occurred without specifying numbers, these were not included in the calculations. Only those complications mentioning specific numbers were included in the analysis. If no complications were said to have occurred or were not mentioned at all they were assumed to be absent. For the occurrence of fetomaternal transfusion only those studies were used in which a Kleihauer test had been performed. Each perinatal death mentioned was studied carefully as far as details were provided. The same was done for all the (emergency) cesareans performed because of version-related complications.

The search produced 166 (Medline) and 140 (Embase) results (December 2002). In total there were 178 hits. Because of language complications, 13 publications were excluded before further screening. Eventually 44 useful articles met the inclusion criteria (11–54). The total number of patients amounted to 7377, ranging from 11 to 923. The mean success rate was 59.2% and ranged between 35% and 100% (43). Of the successfully turned fetuses 5.6% (151/2684) reverted back to breech position. Excluding patients who were lost to follow-up, an average of 80.7% (3200/3967) of all successful versions gave birth vaginally (range 54–97%).

Transient abnormal CTG patterns were reported in 347 (5.7%) cases (235 bradycardia lasting less than 3–5 min, 17 decelerations and 95 nonspecified; tachycardia was not regarded as a complication if [beta]-sympathomimetics were used). In only four patients did these transient changes lead directly to a cesarean. In another 27 (0.37%) cases pathological or persisting CTG patterns were mentioned, leading to a cesarean in 22 cases. In the seven studies performing a Kleihauer test, significant fetomaternal transfusion was found in 18 patients (3.7%). Version-related vaginal blood loss was seen in 35 (0.47%) patients, of whom 17 underwent an emergency cesarean. In 14 cases suspected placental abruption was the reason for this. An actual abruption, however, was only confirmed in six patients, and another three had partial abruption, producing a mean incidence of 0.12%. One of those, however, occurred during oxytocin induction of labor. All children but one, in which there was a significant patient delay, had a good outcome. Umbilical cord complications (0.054% of all ECVs) were reported to lead to an emergency cesarean in three cases and probably caused one stillbirth. The total number of cesareans caused directly by version-related complications amounted to 43, of which 32 (0.43%) were emergency procedures. The neonatal outcome is reported generally as being good, with 5-min Apgar scores below 7 seldom being mentioned. A femur fracture almost certainly caused by external version was reported once only. Perinatal mortality was reported in 12 cases (0.16%).

There were five smaller studies using epidural or spinal anesthesia and one larger study using N₂O inhalation anesthesia that could not be included for those reasons but were otherwise comparable (55–60). Complications in these studies were analyzed separately (Table I).

 

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Table I. Complication rates of external cephalic version (ECV): comparison of ECV with or without anesthesia

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With external version the fetus is manipulated in such a way that after slightly lifting the presenting part the head is moved gently towards the pelvic inlet (forward roll) or, if this does not succeed, the breech is moved away from the pelvis and toward the fundus (backward flip). In his more elaborate description Hofmeyr prefers starting with a backward flip (61,62).

Although ECV had already been used for several centuries, it was applied on a larger scale only by the middle of the last century as the relatively high risks associated with a cesarean made it an attractive alternative (62–64). Initially most version procedures were performed between 32 and 34 weeks as it was thought to be hardly possible to perform after 37 weeks. While this assumption was vitiated in later studies, ECV beyond 37 weeks is supported by some very good arguments as well. Although success rates will be higher because of easier manipulation at a younger gestational age, a fetus may also revert more easily to breech. Reversion rates reported beyond 37 weeks are fairly low, at 1–2% (65). Moreover, the natural tendency for spontaneous version causes steadily decreasing numbers of breech presentations from 10 to 15% at 30–32 weeks to 3–4% at 37 weeks (66). A major convincing argument, however, is avoiding preterm birth if fetal distress caused by version necessitates performing an emergency cesarean. Finally, a systematic Cochrane review suggested that only version at term is efficient (67,68).

Increasing controversy regarding possible version-related adverse effects on the fetus and doubts about efficacy led to a strong decrease in its popularity around 1970. Fetal mortality was thought to be about 1% (69). However, with time, a cesarean had become an increasingly safe intervention for the mother (62,70). Retrospectively, all reported cases of fetal mortality in the preceding period were associated with the use of general or inhalation anesthesia, often as early as 32–34 weeks of pregnancy (71). Many studies have followed since, almost none of them using general anesthesia, and fetal risks are assessed to be fairly small. This is partially ascribed to the introduction of fetal monitoring by means of CTG and to the use of ultrasound throughout the procedure (10,64,65). Despite many studies on the efficacy of ECV, to date the exact risks related to external version remain unclear. The majority of complications are communicated by case reports, thus not elucidating their incidence. Remarkably, in most studies neonatal outcome frequently appears to be good.

To keep potential fetal and maternal risks as low as possible almost all studies currently use the criteria set and contraindications as stated in the guidelines of the ACOG (72). This means performing ultrasound assessment in advance, CTG registration before and after the procedure and, if necessary, administration of anti-rhesus-D immunoglobulins. Facilities to perform an emergency cesarean are a minimal requirement and in several studies patients are kept in a fasting state for that purpose (11–14). External version is refrained from in cases of oligohydramnion, fetal or uterine anomalies diagnosed by ultrasound, placenta previa or unexplained uterine bleeding, a compromised fetus (e.g. growth retardation, hypertensive disease) and multiple gestation. Further contraindications are prelabor rupture of membranes and previous uterine surgery other than using an incision of the lower uterine segment. In some studies a previous cesarean is regarded as an absolute contraindication because of fear for uterine rupture. However, there are several studies succeeding in successful version in a majority of patients in the absence of any serious adverse effects for either mother or fetus (14,15). In older studies an anterior positioned placenta was often considered a contraindication as well, but a more recent study could not find any adverse effect on fetal outcome (16).

The majority of studies currently use tocolytics. A systematic review showed improved success rates without significantly affecting the final number of cephalic presentations, but with a reduced cesarean rate (73). There are no reports on the effects of tocolysis on the complication rate.

From our analysis transient CTG changes appear to be most frequent, with 5.7% of all procedures. This number is lower than the 19% and 36% mentioned in previous studies (17,68), which might be caused partly by underreporting of “innocent” variable decelerations and not including tachycardia in this analysis. A recent study specifically focusing on bradycardia also found a low incidence of 8.4% (18). The occurrence of CTG changes such as transient bradycardia or decelerations is a frequently mentioned complication that seldom leads to the necessity of a cesarean. A transient decreased variability supposedly not originating from the use of tocolytics is also often seen after ECV (19,74). All these CTG changes are thought to be a normal physiological reaction of the healthy fetus to stress caused by transient relative hypoxia as a result of a version procedure (74,75). This assumption seems to be confirmed by Doppler measurements before and after external version (76). Nevertheless, careful fetal monitoring is mandatory in all cases as a transient bradycardia could also be a sign of compromised fetal condition (18,76). Generally nearly all CTG patterns will have normalized within 1 h after version (77). Only incidentally (0.37%) evident pathological or persisting mild changes are reported. These changes, however, led in the majority of 27 cases to an intervention; two fetuses were reverted, 12 (emergency) cesareans were performed and another nine within 48 h of version. In addition, one patient had labor induction (because of persisting tachycardia, eventually leading to partial placental abruption and an emergency cesarean).

Vaginal bleeding has been reported in several studies. The incidence is reported to vary from 0 to 9% and occurs particularly with the use of general anesthesia (69). In studies where only tocolytics were used, the incidence of vaginal bleeding was about 0.8%, comparable to the 0.47% found in this review. Although it mostly concerns isolated asymptomatic bleeding, the possibility of placental abruption caused by manipulation of the uterus remains and has been reported in several publications. Therefore, and especially if combined with other symptoms suspicious for placental abruption, vaginal bleeding has led to an emergency cesarean in 40% of the cases. However, the incidence of placental abruption (0.12%) is fairly low. Compared to the incidence of 0.34% in a general term population it does not seem to occur more often after an ECV procedure (78). Because of an allegedly higher risk for placental abruption or fetomaternal transfusion, an anterior placental site has been regarded a (relative) contraindication by some authors (75). However, a clear causal relationship between placental site and the occurrence of these complications has not been proved (79).

An issue closely related to this is the occurrence of fetomaternal transfusion caused by ECV. This complication has seldom been investigated systematically, but in two reviews an average incidence of about 2.4% was found (10, 79). Looking at the studies in our analysis a value of 3.7% was calculated. Almost all cases (16/18), however, are derived from one study, in which the author already addresses his concerns about the accuracy of data collection (20). Leaving this study out would result in an incidence of only 0.5%. A more recent study of 116 external versions on 114 women found no difference in Kleihauer levels before and after the procedure, which is comparable with the results of another, similar study (21, 79). A case report describing fatal neonatal anemia allegedly caused by fetomaternal hemorrhage following ECV was combined with epidural anesthesia and had a Kleihauer test performed only after an emergency cesarean. Moreover, there were no signs of placental abruption (80). Another case was associated with a placenta on the anterior wall and the use of nitric-oxide inhalation anesthesia (81) and there are also reports of fetomaternal macrotransfusion after spontaneous version (82,83).

In our entire analysis four cord accidents were reported: one funic cord, two cord-related CTG changes after version and one stillbirth (13,22, 84). Some studies have suggested a possibly endangering fatal cord entanglement to be caused by manipulations during external version. It is probably just as likely that external version will be unwrapping a preexisting loop as that it will cause an entanglement (63). Within a large group of patients undergoing ECV the incidence of entanglement at time of labor (21%) was lower than in the control group (23). Moreover, the incidence of entanglement at time of delivery in an unselected population with cephalic presentation is about 25% (85). There is also no causal relationship between umbilical entanglement and stillbirth (85) and it does not appear to affect fetal outcome or rates of operative (vaginal) delivery (86). Although reported in the past, the incidence of true knots in a general population is so small that complications related to version procedures are probably not to be expected (87,88). The risks of cord accidents seem therefore low or even absent and may be negligible compared to the higher risks of cord prolapse if membranes rupture in breech or transverse presentation (10,24). Because of the typical position the fetus often assumes after successful version (arms in front of the head while not yet fully engaged), the umbilical cord is said to be more liable to prolapse if membranes rupture in the first hours after the procedure (25,89,90). Thus ECV in early labor is often considered to be a contraindication.

Although Zhang et al. reported that perinatal death related to external version had not occurred in the US since 1980 (10), nine studies in our analysis report 12 cases of perinatal death. When categorized as proposed in a recent review (91), three of those definitely did not result from the procedure as there was one chromosomal defect (48), one child with congenital pulmonary hypoplasia (47) and another child with congenital cerebellar hypoplasia (33). Two further cases of intrauterine fetal death were not related in time, occurring several weeks after uncomplicated version (18,37). There were two stillbirths most probably related to the external version. However, in both cases patient delay and noncompliance might have contributed considerably to the adverse outcome (23,50). The remaining five cases could be categorized as “unexplained”– possibly caused by ECV but occurring in any large cohort as well (22,35,49). Nevertheless, these numbers produce an incidence of 1.63 in 1000 version procedures. This is not higher than the fetal death rate in a low-risk pregnancy population between 36 and 40 weeks, which is 6.2 per 1000 births (92).

All other complications that might occur are based on case reports. These often concern unusual and rare complications. Such a complication is the version-related femur fracture in one of the analyzed studies (25). Another reported case relates to a cervical spinal cord transection possibly caused by a version procedure (93). Compound presentation during labor after successful version has been reported several times and seems to occur only rarely (94). A once postpartum diagnosed old intracranial hemorrhage ascribed to an earlier successful ECV could retrospectively be demonstrated on the videotaped ultrasound screening prior to version (95).

Overall it seems that complications as they had been reported in studies around 1970 nowadays seem to be far less frequent. A major cause is probably abandoning the use of anesthesia. Previous studies have suggested lack of pain signals as a warning of too much force applied as a reason for more serious complications (71,96). Analyzing separately the studies using anesthesia seems to confirm this assumption with complication rates that are 2–10 times higher (Table I). More uniformity in applying certain guidelines and contraindications also seems to have affected the occurrence of complications. It remains unclear what role the current almost universal use of tocolytics has in this respect. All this makes ECV in selected cases an attractive and apparently safe alternative for primary cesarean in breech presentation. However, even though it becomes clear that risks seem to be smaller than in the past, external version is a procedure subject to strict rules and only suitable for a clinical situation.

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Key words: external cephalic version; breech; fetal; safety; risks