Introduction

Impacted fetal head at caesarean birth is an obstetric emergency that transforms an apparently straightforward operation into one that is both technically challenging and stressful, with the potential for serious maternal and/or fetal harm. This scenario is most often encountered when a decision is made to perform a caesarean delivery late in advanced labour, particularly at full cervical dilation, when the fetal head may have descended deeply into the pelvis. This complication can however occur at any stage of labour, especially if labour has been prolonged, the uterus is opened during a contraction, or the fetal head is malpositioned or preterm. A useful contemporary definition is the inability to deliver the fetal head with the surgeon’s dominant hand, requiring additional manoeuvres, surgical extensions, and/or tocolysis to disimpact and achieve delivery.¹

The consequences of an impacted fetal head can be significant. Maternal complications include uterine incision extensions that increase blood loss, result in injury to the bladder and/or ureters, and increase the risks of postoperative infection. Neonatal complications include hypoxic-ischaemic injury from delayed delivery, skull fracture, or intracranial haemorrhage (or other birth trauma such as limb injury) due to excessive force in attempts to extract the fetus.^1-4

While many instances of impacted fetal head seem unpredictable, pausing to review the overall circumstances when deciding to perform a caesarean delivery are warranted, thereby allowing all members of the operating room team to prepare for their roles. A fundamental consideration is that the fetus has oxygen delivery reserves and thus can withstand delays in delivery. In most instances, they are at greater risk of physical injury from panicked forceful efforts to be delivered than from a modest delay in delivery. The principles of safe delivery of the infant in this context including pausing at uterine exposure with adequate access, knowledge of the fetal station and position, ensuring that the uterine incision is only made during relaxation, introduction of the surgeon’s hand to effect fetal flexion, and being mindful of the series of additional steps to calmly undertake if the fetal head is discovered to be impacted.

Is Caesarean Birth the Correct Decision?

Where assisted vaginal birth cannot be safely performed in the delivery room, inherent delays from “decision to incision,” including patient transfer to the operating theatre and epidural top-up, can result in descent and rotation of the fetal head, such that vaginal birth becomes possible – especially when the patient is placed in the lithotomy position. This is particularly true in multiparous patients. Failing to recognise such labour progress results in a high risk of impacted fetal head at caesarean birth and is easily avoided by embedding this rule into clinical practice. There is no substitute for careful abdominal and vaginal examination when the patient has been adequately topped-up with analgesia; if there is any sense of progress, awaiting the next contraction and assessing progress with pushing may convert a potentially very challenging caesarean birth into a relatively straightforward forceps or vacuum-assisted birth.

Anticipate and Prepare Prior to Making the Uterine Incision

Impaction is more likely in cases of prolonged labour, advanced cervical dilatation, low fetal station, malposition, significant caput or moulding, prematurity, and unsuccessful attempts at assisted vaginal birth.^2,3 The absence of these risk factors never excludes the risk of impacted fetal head, especially at full dilation, therefore heightened awareness is the best method of mitigating against this complication. As such, the first step is to inform the interdisciplinary team that difficult fetal extraction may be encountered. The surgeon should ensure that experienced assistance is available, including someone competent to perform gentle flexion and vaginal disimpaction between contractions, should this be requested. The identified assistant should wear sterile gloves, and the patient should be placed in the frog-leg or modified lithotomy position, facilitating rapid and easy digital access to the vagina. Appropriately trained personnel should be present in the room in anticipation of needing active neonatal resuscitation. The anaesthetist should anticipate a potentially longer operation, increased blood loss, need for Trendelenburg tilt, and possible need for acute tocolysis.³ All of these considerations should be in place prior to the incision and be included in the surgical briefing to ensure all team members are aware and prepared.

Maternal positioning is important. In addition to a modified lithotomy or frog-leg position, lowering the operating table or providing an appropriate step for the surgeon can improve the direction (by switching hands) in which force is applied during gentle disimpaction.³ This preparation takes only a few minutes and ensures improved access during the surgery. Skipping important preparation steps can result in considerably longer time spent repairing an uncontrolled lateral hysterotomy extension, or other complications.

Start with Space

At full dilation, the lower uterine segment may be markedly elongated, thin, and distorted. The bladder and cervix may therefore be displaced superiorly. Development of a bladder flap and subsequent uterine incision made too low risks entering the cervix or even the upper vagina.³ Therefore, the surgeon should consider making the transverse hysterotomy relatively high, at or just above the bladder reflection, and within the distended lower segment to avoid injury to the cervix or vagina.³ To facilitate this, the abdominal and uterine incisions need to be sufficiently large. Trying to deliver an impacted head through inadequate exposure encourages progressively greater force.

Once the hysterotomy has been made, make a thorough manual assessment before forces are employed to achieve delivery. Where are the fetal head and shoulders? How can you optimally flex the fetal head? Can a hand easily pass between the head and maternal pelvis? Is the uterus tightly contracted around the fetus? If the answer to the last question is yes, wait and allow the uterus to relax between contractions – usually one to two minutes after the initial uterine incision. If relaxation remains inadequate after a contraction, short-acting intravenous or subcutanous tocolysis may facilitate disimpaction, although evidence regarding its effectiveness and safety specifically for impacted fetal head remains limited.^1,2

The instinct created by fetal compromise is understandably to move faster. Paradoxically, haste at this point can delay birth by causing uterine trauma and making extraction more challenging.

Flex Before You Elevate

When cephalic extraction is possible, the surgeon should aim to pass the hand over the occiput, thereby flexing the fetal head, before elevating it. Applying upward pressure to a deflexed head may further extend the fetal neck and increase the presenting diameter, making continued attempts at delivery more challenging and risking uterine extensions.³ If the surgeon’s hand cannot pass beneath the head easily, repeatedly forcing it into the pelvis will likely result in further uterine extensions, potential fetal head injury, or bladder damage. A useful next move in this context is to wait for the uterus to relax, then elevate both fetal shoulders to disengage the head sufficiently to allow the hand to pass over the occiput.^3,4 If this fails, consider the following alternative strategies rather than repeating unsuccessful manoeuvres with increasing force.

Push, Pull, or Shoulders First?

Several techniques can be used to disimpact the fetal head.

1. Vaginal disimpaction (“push” technique)

This approach requires a skilled and senior assistant to place a hand vaginally and elevate the head towards the uterine incision. The hand and splayed fingers should cup the fetal head, promoting flexion and always distributing pressure broadly.³ A few fingers pushing against a small area of the skull is less effective, has far greater focal force on the skull bones, and is therefore potentially traumatic. As such, this dictates that the most experienced trained personnel available should be identified and in place prior to making the uterine incision.

2.Reverse breech extraction (“pull” technique)

Rather than trying to deliver the fetus from its cephalic presentation, the operator changes strategy and – when the uterus is relaxed – carefully reaches upwards towards the fundus, identifying and delivering the fetal feet, followed by delivering the trunk, shoulders, and finally the head. Patience is key – fetal oxygenation is protected by the physical properties of HbF that continues to deliver oxygen to the fetal brain at progressively lower oxygen tensions – therefore the surgeon should have sufficient time to pause, await adequate relaxation of the uterus to gently locate the feet, and begin reverse breech extraction, as opposed to rushed forceful movements on a contracted uterus. Extension of the hysterotomy, for example as a J or inverted-T incision, may rarely be required to provide safe access.^3,5 Reverse breech extraction may be an ideal solution for the impacted occiput-posterior fetal head because the fetal limbs are positioned anteriorly and are readily accessible.

3. Patwardhan technique

This technique is a variation on the pull technique and may be used when the fetus is in an occiput anterior position. Here the impacted fetal head is overcome by delivering each arm and shoulder, followed by fundal pressure. Then, as the fetus flexes, the surgeon’s hands envelope under the armpits and thorax, flexing the body to deliver the buttocks, followed by the head.⁶ Ensuring more lateral space at the fascial layer and stretching the incision may allow the surgeon to more easily complete these manoeuvres. This sequence is counterintuitive and therefore requires specific simulation training. It is less familiar in many Australasian, European, and North American units than in Africa or South Asia, where it was originally described.

Earlier systematic reviews suggested reverse breech extraction may reduce uterine extensions, haemorrhage, and other maternal complications compared with vaginal disimpaction. However, a 2024 systematic review found the available comparative literature to be at significant risk of bias and concluded that the evidence is insufficient to establish superiority of any single technique.⁴ The contemporary message is therefore that clinicians should be safely trained in multiple disimpaction techniques and able to move appropriately between them based on the clinical situation.^1,4

Disimpaction Devices

Cephalic elevation devices such as the Fetal Pillow® (CooperSurgical, Trumbull, CT, USA) or Tydeman® Tube (Rocket Medical, Guy’s and St Thomas’ NHS Foundation Trust) are intended to elevate the fetal head from below during vaginal disimpaction techniques. Initial studies exploring the Fetal Pillow® device suggested reductions in uterine extensions and delivery time. However, an influential randomised trial of the Fetal Pillow® was retracted, materially changing the evidence base.⁴ Current systematic review evidence does not support a confident conclusion that prophylactic use of elevation devices improve important maternal or neonatal outcomes.¹^,4 The use of equipment or instruments not intended for disimpaction, including the use of a vacuum delivery device, should be avoided as fetal injury has been reported.

Once the Baby is Delivered, Examine the Uterus Carefully

After the baby has been delivered, careful inspection of the hysterotomy for lateral and inferior extensions is important. Exteriorisation of the uterus may improve visualisation to ensure no injuries are missed. If an extension tracks inferiorly, mobilising the bladder may be required to identify its apex and exclude urinary tract injury.^1,4

Furthermore, particularly after a difficult extraction, consider the possibility of neonatal trauma. For this reason, neonatal team attendance is important prior to delivery of the baby.

Finally, documentation should clearly describe the impaction, manoeuvres used, uterine extensions or additional incisions, maternal or neonatal complications, and any implications for future pregnancy.^3,5 Debriefing the patient and family is equally important, as this may have been a frightening or unexpected outcome for parents and their support people.

The Most Important Manoeuvre is Preparation

No single technique will resolve every impacted fetal head. The fetal position, degree of impaction, uterine tone, surgical exposure, and experience of the team all influence what will work. The safest obstetrician is therefore not necessarily the one with a favourite manoeuvre – it is the one who anticipates difficulty, creates adequate space, understands the mechanics of fetal disimpaction, recognises early when a technique is failing, and is comfortable moving on to another.

When the head will not deliver: slow down, make space, flex before elevating, avoid escalating force, and have an alternate plan. Careful preparation with all team members will reduce the risk of encountering difficulties and is time worth spending prior to any incision. These steps are summarised in the flow chart in Figure 1.