Compound fetal presentation

INTRODUCTION — Compound presentation is a fetal presentation in which an extremity presents alongside the part of the fetus closest to the birth canal. The majority of compound presentations consist of a fetal hand or arm presenting with the head [1]. This topic will review the pathogenesis, clinical manifestations, diagnosis, and management of this uncommon intrapartum scenario.

INCIDENCE — Compound presentation has been reported to occur in 1 in 250 to 1 in 1500 births [2-5]. This is a crude, wide estimate because transient cases are not consistently recognized, documented, or reported.

PATHOGENESIS AND RISK FACTORS — A variety of clinical settings can lead to compound presentation via different pathways. Compound presentation may occur when:

●The fetus does not fully occupy the pelvis, thus allowing a fetal extremity room to prolapse. Predisposing factors include early gestational age, multiple gestation, polyhydramnios, or a large maternal pelvis relative to fetal size [2,3].

●Membrane rupture occurs when the presenting part is still high, which allows flow of amniotic fluid to carry a fetal extremity, umbilical cord, or both toward the birth canal.

●During external version, a fetal limb (commonly the hand/arm, but occasionally the foot) becomes "trapped" below the fetal head and thus becomes the presenting part when labor ensues [6-8].

●The head of the first twin and an extremity of the second twin present together within the birth canal, but this is rare.

CONSEQUENCES — The large irregular presenting part of a compound presentation can result in:

●Dystocia.

●Cord prolapse, which was reported in 15 and 23 percent of patients in two series [2,9].

CLINICAL PRESENTATION

●Compound presentation may present as an incidental finding on ultrasound examination [10].

●Antepartum or intrapartum digital examination through a partially dilated or effaced cervix may detect an irregular shape beside or in advance of the head or breech.

●Intrapartum, the head may remain persistently unengaged after membrane rupture and deviated from the midline [9]. Active phase protraction or arrest of labor may occur. In the second stage, arrest of descent may be associated with a variant of compound presentation in which the fetal hand fills the space between the head and the maternal sacrum [11].

DIAGNOSIS — The diagnosis of compound presentation is based on identification of one or more fetal extremities presenting alongside or in front of the head or buttocks on physical or ultrasound examination [10].

On physical examination, a foot can be distinguished from a hand by its three bony protuberances (calcaneus, lateral and medial malleolus), the angle at the level of the calcaneus, and the toes, which are short and lie in the same line with no opposing thumb.

Differential diagnosis — When a fetal extremity is the presenting part on physical examination, differential diagnosis includes:

●Compound presentation

●Transverse lie with prolapse of an extremity

●Footling breech presentation

An accurate diagnosis is easily made by ultrasound examination or more thorough abdominal and vaginal examinations.

MANAGEMENT

Antepartum management — Antepartum identification of compound presentation usually does not require any interventions or monitoring.

If noted on ultrasound examination immediately following an otherwise successful external cephalic version, the compound presentation will usually resolve spontaneously. In this setting, if a foot or hand is preventing the head from settling into the inlet, vibroacoustic stimulation can prompt fetal movement sufficient to resolve the problem.

If a compound presentation is identified on ultrasound examination in a patient with polyhydramnios, the patient should be counseled on the risks of a prolapsed umbilical cord and fetal extremity when membranes rupture. (See "Umbilical cord prolapse", section on 'Anticipation and prevention of cord prolapse'.)

Intrapartum management — Approaches to intrapartum management are based on patient-specific factors, clinical experience, and insights from case reports and small series, given the infrequent occurrence of this problem. High-quality data to guide management are not available.

For patients with normally progressing labor, we favor observation alone. Some authorities suggest attempting to gently reposition the fetal extremity, while others discourage this practice [3-5,9,12]. We favor expectant management because sometimes the presenting part will push the extremity aside or the fetus will retract the extremity as labor progresses, allowing a large majority of compound presentations to deliver vaginally. A compound presentation involving the arm is more likely to resolve than one involving the foot [4]. We choose to not pinch the presenting part in an attempt to provoke the fetus into withdrawing the presenting part, although this practice is not likely to be harmful.

If the compound presentation persists, descent of the presenting part in the second stage could slow or stop, unless the fetus is extremely small. Manipulation is reasonable in this setting. The author gently pushes the small part up into the uterine cavity with his dominant hand while simultaneously applying gentle fundal pressure to effect descent of the head with his other hand. If this gentle maneuver does not resolve the compound presentation and abnormal progress of labor, the author has a low threshold for proceeding to cesarean birth because of the increased risk for obstructed labor and an adverse outcome (see 'Outcome' below). Oxytocin augmentation should be avoided as it may lead to uterine rupture [2,7]. Forceps- or vacuum-assisted vaginal birth should also be avoided, with possible rare exceptions in which clinical judgment suggests this approach would be faster and safer than an urgent cesarean birth.

OUTCOME — In most cases managed by contemporary standards, labor results in an uncomplicated vaginal birth. Historically, however, high mortality rates were reported and were related to prolonged obstructed labor, internal podalic version and extraction, uterine rupture, prolapsed cord, and complications of preterm birth.

No large contemporary series of compound presentation have been published. The following case reports, and others, underscore the need for cesarean birth if the compound presentation does not resolve spontaneously or with gentle pressure in cases of protracted labor. However, it should be noted that only complicated cases prompt publication of a case report [13-15].

●One case report of a patient with a compound presentation and protracted labor described ischemic necrosis of the arm, which was attributed to entrapment of the fetal arm between the head and bony pelvis; limb amputation was required [13].

●Another case report described a similar occurrence with a dramatic appearance of limb ischemia (picture 1), but recovery occurred without the need for amputation [15].

●A third case report described a vacuum-assisted birth in which an unrecognized compound presentation resulted in a maternal rectal laceration; the fetal hand was found to be protruding through the anus as the head was crowning [14].

If neonatal compartment syndrome occurs, some authorities recommend urgent fasciotomy, which may salvage the limb. (See "Pathophysiology, classification, and causes of acute extremity compartment syndrome", section on 'Birth injury'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Labor".)

SUMMARY AND RECOMMENDATIONS

●Clinical findings and diagnosis – Compound presentation may be an incidental finding on an antepartum ultrasound examination or it may be palpated as an irregular shape beside or in advance of the vertex or breech during digital cervical examination. The diagnosis is based on identification of one or more fetal extremities presenting alongside or in front of the head or buttocks. (See 'Clinical presentation' above and 'Diagnosis' above.)

●Epidemiology – Persistent compound presentation is rare once active labor is established. Predisposing factors include preterm birth, multiple gestation, polyhydramnios, a large maternal pelvis, external cephalic version, and rupture of membranes at high station. (See 'Incidence' above and 'Pathogenesis and risk factors' above.)

●Management

•Antepartum – Antepartum identification of compound presentation usually does not require any interventions or monitoring other than patient education about the finding. (See 'Antepartum management' above.)

•Intrapartum – For compound presentations with normal progress of labor, we suggest expectant management rather than intervention (Grade 2C). Most cases will resolve spontaneously or will have vaginal births even without resolution. (See 'Intrapartum management' above.)

A persistent compound presentation can result in dystocia. If descent of the presenting part in the second stage becomes protracted or arrests, we gently push the small part up into the uterine cavity with the dominant hand while simultaneously applying fundal pressure with the other hand to effect descent of the vertex. If the compound presentation and labor abnormality do not resolve after this gentle maneuver, we have a low threshold for proceeding to cesarean birth. Oxytocin augmentation should be avoided as it may lead to uterine rupture. (See 'Intrapartum management' above.)

ACKNOWLEDGMENTS — The UpToDate editorial staff acknowledges Edward R Yeomans, MD, and Clint M Cormier, MD, who contributed to earlier versions of this topic review.