Cesarean section is commonly perceived as a simple and safe alternative to difficult vaginal birth. However, several trends in obstetrical practice may act in concert to cause impaction of the fetal head during the second stage of labor or, more commonly, following failed instrumental delivery. Subsequently, difficult and potentially traumatic disengagement of the deeply wedged head during cesarean section occurs.
A deeply impacted fetal head (IFH) encountered at the time of cesarean delivery is estimated to occur during 1.5% of all cesarean deliveries worldwide and 25% of emergency cesarean deliveries. Risk factors for an IFH include fetal malposition, a prolonged second stage of labor, and failed trial of operative vaginal delivery. The risk of an IFH is one underlying factor contributing to the morbidity associated with second stage cesarean deliveries such as; blood loss of more than 1000 mL, blood transfusion, and intraoperative trauma (hysterotomy extension, laceration of the uterine artery, or injury to the bladder, ureter, or bowel).
Described complications of an IFH include inferior or lateral hysterotomy extension into the cervix, vagina, or broad ligament; injury to the bladder or uterine blood vessels; maternal hemorrhage; endomyometritis; wound infection; low neonatal Apgar scores; neonatal intensive care unit admission; and fetal injuries (e.g., long-bone fracture, skull fracture, or fetal laceration).
The proportion of cesarean deliveries performed in the second stage of labor is projected to increase for several reasons. First, there has been a decline in the use of rotational and midpelvic forceps delivery. Operative vaginal delivery rates have decreased in general with a shift toward vacuum-assisted vaginal delivery. Second, there is a national trend toward increased utilization of regional analgesia, which can prolong the duration of the second stage. Finally, contemporary practice guidelines intended to decrease the primary cesarean delivery rate have proposed lengthening the permissible duration of the second stage of labor; the Obstetric Care Consensus “Safe Prevention of the Primary Cesarean Delivery” endorsed by both the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine recommends that nulliparous women be allowed 3 hours and multiparous women 2 hours for pushing without epidural analgesia. A longer duration may be allowed in women receiving epidural analgesia. The increasing prevalence of maternal obesity and fetal macrosomia could also contribute to the incidence of IFH.
Several factors contribute to the mechanism of dystocia in delivery of a fetus with an IFH. The lower uterine segment is often distended, potentially risking cervical or vaginal incision or hysterotomy extension with significant blood loss. Only the fetal shoulder may be visible once the uterine cavity is entered (the “shoulder sign”) or the fetal head may be significantly deflexed and/or molded. Finally, the surgeon’s ability to minimize the delivering cephalic diameter by intentional flexion may be limited by splinting of the fetal spine within a contracted uterus. Faced with this challenging context, the surgeon must rapidly elect an efficient and effective delivery technique. This article reviews the available evidence concerning techniques for disengagement of the IFH and the institutional management algorithm proposed for clinical application as described by JB Manning et al.
Several techniques have been described for disengagement of the IFH, the most common of which are the “push” and “pull” methods.
The push method of cephalic replacement has been the favored technique in the Unites States and United Kingdom since the 1980s. In this method, the woman is placed in a modified lithotomy position with knees flexed and thighs abducted. An assistant in sterile gloves inserts a hand into the vagina and gently replaces the fetal head superiorly into the pelvis with cupped fingers as the surgeon applies traction to the fetal shoulders or attempts to flex and elevate the head into the hysterotomy.
The pull method, or reverse breech extraction, has been studied increasingly over the last decade in several developing countries where obstructed labor is more common. In this method, following hysterotomy, the surgeon reaches toward the upper uterine segment, grasps 1 or both fetal legs, applies gentle traction until the second leg appears, and gently delivers the fetus by both legs, as with a combination of internal podalic version and footling breech delivery. Breech delivery may be accomplished through a low transverse hysterotomy; however, utilization of a low vertical or low transverse uterine incision with possible extension into an inverse T or J shape to maximize space has been described.
Alternative techniques are less commonly described and include the bimanual push method, Patwardhan technique, and the Foetal Disimpacting System. The bimanual push method is a technique in which the surgeon, rather than an assistant, elevates the fetal head with a hand from below while simultaneously elevating the head with their uterine hand. The Patwardhan technique was originally described in India during the 1950s and involves delivery of the fetal shoulders first, followed by fetal trunk and then feet. In 2008, a new technique called the Foetal Disimpacting System was described, which uses a saline balloon placed inside the vagina to elevate the fetal head up to 3 cm.
Evidence Comparing the Push and Pull Methods
Several prospective studies have compared the push and pull methods. Berhan and Berhan summarized available evidence comparing the push and pull methods in a systematic review and meta-analysis; they included 11 studies and 1028 total deliveries from 7 Middle Eastern, African, and South Asian countries. They reported that the push method was associated with a nearly 8-fold increased risk of inferior and/or lateral hysterotomy extensions, higher estimated blood loss, greater need for blood transfusion, and an increase in mean operating time. Rates of wound infection were not statistically different. There were 3 total long-bone fractures in the pull group (2 femoral and 1 humeral) and none in the push group; in addition, there was 1 humeral fracture in the Patwardhan group. Pooled data revealed no significant difference in 5-minute Apgar scores between the groups.
- The meta-analysis of Berhan and Berhan is limited by variation in the intervention (delivery technique) across studies; 3 studies compared pull with conventional methods (without the push method), and 2 studies compared the Patwardhan technique with conventional methods.
- Another barrier to applying these results to clinical practice is the lack of consistent reporting of need for hysterotomy extension into the contractile portion of the uterus. Furthermore, none of the studies were conducted in Western or European countries, thus limiting generalizability to these populations.
Evidence for Alternative Delivery Techniques
Two recently published case series report on alternative fetal disengagement methods. Singh and Varma presented 30 cases in which a vaginal saline balloon, the Foetal Disimpacting System, was used for elevation of the fetal head; the device was successful in disengaging the fetal head in all reported cases without any maternal or fetal injuries.
Shazly and colleagues described “Shazly’s step,” abdominal disimpaction with lower uterine segment support, in a series of 15 women. Of the 15 cases, there was only 1 lower segment extension of less than 2 cm (6.7%), 1 case requiring blood transfusion (6.7%), and no fetal injuries. Both series used a low transverse hysterotomy.
However, one should consider that if the fetal head is deflexed, applying pressure in the wrong direction may worsen deflexion and impaction, making abdominal delivery even more difficult. In addition, some clinicians question the practical ability of a saline-filled balloon to disimpact the head of a fetus weighing several kilograms.
Algorithm for Managing an IFH
Existing data do not clearly favor a singular delivery technique. JB Manning et al suggest the surgeon utilize the technique (or series of techniques) of greatest familiarity. Regardless of the disengagement technique selected, situational awareness, clear communication, rapid and decisive operative maneuvers, and effective multidisciplinary teamwork among operating room staff are essential for safe and prompt management of an IFH. In an effort to improve maternal and neonatal safety and promote standardization of approach, we have implemented “ALERT” algorithm into our obstetrical practice for the management of an IFH.
“ALERT” mnemonic for the management of an IFH at the time of cesarean delivery:
A: Alert the multidisciplinary team early if an impacted fetal head is suspected.
L: Lower the operating table to facilitate maneuvers. Consider Trendelenburg position (maternal head down).
E: Extend the skin, fascial, or uterine incisions if needed after assessment.
R: Relax the uterus. Administer uterine relaxants or incise Bandl ring if present.
T: Techniques for delivery. Consider: The “Push” method or The “Pull” method
The “Push” method
- Elevate the fetal head using a vaginal hand.
- Rotation and flexion may be needed; exercise cautions to not cause skull depression/fracture.
The “Pull” method (reverse breech extraction)
- Grasp fetal feet and deliver through hysterotomy followed by torso/shoulders and, finally, fetal head.
- Hysterotomy extension may be required.
Delivery of an Impacted Fetal Head During Cesarean: “Algorithm for the management of an IFH at the time of cesarean delivery”
The critical first step is anticipation of the problem in cases of prolonged second stage of labor, particularly if attempts at operative vaginal delivery have been unsuccessful. Preparations should be made for additional surgical assistants and anesthesiology personnel. The anesthesia team should have uterine relaxants available (e.g., nitroglycerine or terbutaline). The hysterotomy should be made at the upper portion of the lower uterine segment to reduce the possibility of inferior extension into the cervix/vagina or lateral into the broad ligament. Recognition of the “shoulder sign” upon entry into the uterine cavity (i.e., the fetal shoulder at the level of the hysterotomy) should alert the surgeon to the possibility of an IFH.
Once an IFH is recognized, the surgeon should communicate clearly with operating room staff, and if the push method is elected, appropriate ancillary staff should be designated. Next, the operating table should be lowered to allow for disengagement maneuvers with consideration of Trendelenburg positioning. Adjunctive pharmacologic uterine relaxation with nitroglycerine or a β2-adrenergic agonist may be useful if the uterus is contracting. In addition, the hysterotomy should be assessed for adequacy and extended superiorly with bandage scissors if deemed necessary. Finally, the push or pull method for fetal disimpaction should be performed.
Review of the available evidence suggests that the pull method for management of an IFH may result in fewer hysterotomy extensions, lower blood loss, and shorter operating time. However, high-quality evidence is lacking. The risk of incidental hysterotomy extensions associated with the push method must be weighed against the possible need for intentional T or J extension for the pull method, which has implications for uterine rupture and the ability to labor in future pregnancies.
Although both methods may cause serious maternal and neonatal complications, available data seem to favor the pulling method and better outcome seems to depend on adequate uterine relaxation, the patient’s position during operation, and special attention to the uterine incision. More data are needed to establish the frequency and extent of intraoperative disengagement dystocia and to determine the management protocol that carries the lowest risk in such circumstances.
At present, the first-line approach for an IFH should be based on individual familiarity with each technique; ideally, surgeons would be trained in several different techniques. In conclusion, an IFH at the time of cesarean delivery is a challenging clinical scenario that may become more common secondary to a decrease in the performance of operative vaginal deliveries and extension of the acceptable duration of the second stage of labor. Further study of fetal extraction techniques is warranted to develop evidence-based recommendations.