Fetal teratomas and the path from prenatal debulking to delivery planning

Fetal teratomas represent a rare but clinically significant group of congenital neoplasms that arise from totipotent germ cells and can grow in the sacrococcygeal region, the neck, the oropharynx, the mediastinum, or, less commonly, intracranially. Although most are histologically benign, their biological behaviour in utero can be aggressive, producing mass effect, hydrops fetalis, cardiac failure, and polyhydramnios. For perinatal teams in Australia, where geography often separates families from tertiary fetal medicine centres in Sydney, Melbourne, Brisbane, or Perth, anticipating the trajectory of these lesions is essential for safe delivery planning.

A coordinated approach that brings together maternal-fetal medicine specialists, paediatric surgeons, neonatologists, anaesthetists, and dedicated nursing staff is widely accepted as the standard of care. Prenatal debulking, when offered, is reserved for highly selected cases where the tumour threatens fetal viability or the airway before birth. Delivery planning then becomes a detailed choreography of timing, mode, location, and immediate postnatal support. The remainder of this article walks through the diagnostic pathway, the decision points for in-utero intervention, the techniques available for tumour reduction, and the practical considerations for delivery in a high-resource setting.

Understanding fetal teratomas and their behaviour in utero

Teratomas are germ cell tumours containing elements from all three embryonic layers, and the fetal variants most often encountered by perinatal teams are sacrococcygeal teratomas, cervical teratomas, and oropharyngeal or epignathus lesions. The pathophysiology in utero differs from postnatal disease because the tumour competes with the fetus for cardiac output. A large vascular tumour can act as an arteriovenous shunt, raising preload, driving high-output cardiac failure, and eventually producing hydrops. Polyhydramnios from impaired fetal swallowing and preterm labour are common secondary findings.

The natural history is heterogeneous. Some teratomas grow slowly and remain amenable to postnatal resection, while others enlarge rapidly between the late second and third trimesters. Solid lesions with high vascularity tend to behave worse than predominantly cystic ones, and a tumour-to-fetal-volume ratio above a critical threshold has been associated with worse outcomes in several cohorts. Maternal complications such as mirror syndrome, where the mother develops oedema and hypertension mirroring the sick fetus, are an additional concern and warrant close surveillance of blood pressure and renal function.

Prenatal diagnosis and imaging surveillance

Most fetal teratomas are first suspected on routine morphology ultrasound, which in Australia is typically performed between 18 and 22 weeks under Medicare-funded obstetric care. A sacral mass, a neck mass distorting the airway, or an oropharyngeal lesion displacing the tongue are the most recognisable appearances. Doppler interrogation reveals vascularity and helps estimate shunt volume, while measurement of the cardiac circumference, combined Doppler indices, and middle cerebral artery peak systolic velocity are used to gauge fetal wellbeing.

Magnetic resonance imaging is increasingly used as a complementary tool. Fetal MRI provides superior tissue contrast, clarifies the relationship of the tumour to the airway, lungs, and great vessels, and is particularly valuable when planning an ex-utero intrapartum treatment procedure. In Australia, access to fetal MRI is concentrated in tertiary perinatal centres, and referrals from rural and remote areas sometimes require transfer to a metropolitan fetal medicine unit. Counselling should incorporate the limits of imaging, the possibility of rapid growth between scans, and the option of serial monitoring every one to two weeks when a lesion is high-risk.

Indications for fetal intervention

The threshold for prenatal intervention is intentionally high. Most fetal teratomas can be delivered and resected after birth, and the risks of open fetal surgery are not justified when expectant management is reasonable. Intervention is generally considered when there is evolving hydrops, severe polyhydramnios threatening preterm delivery, a tumour so large that it obstructs delivery, or evidence of progressive cardiac compromise. Counselling in these scenarios benefits from a second opinion at a quaternary centre, ideally one with active fetal surgery programs.

Australian perinatal teams frequently collaborate across state borders for these rare cases, drawing on experience at centres in Brisbane, Sydney, and Melbourne. Where in-utero intervention is being weighed, a documented multidisciplinary discussion involving maternal-fetal medicine, paediatric surgery, neonatology, anaesthetics, and bioethics is recommended. The family must be counselled about the possibility of fetal or neonatal demise, the risk of maternal morbidity from laparotomy or hysterotomy, and the implications for future pregnancies.

Comparing prenatal debulking strategies

A range of techniques has been described for reducing tumour burden before birth. The choice depends on the location of the lesion, its vascularity, gestational age, and the expertise of the team. Minimally invasive approaches suit predominantly cystic lesions, while highly vascular solid tumours may require more sophisticated techniques or a decision to proceed straight to delivery.

The summary above should be read as a starting point for discussion rather than a rigid algorithm. Many centres in Australia would only offer the most invasive options after a documented second-opinion process, and outcomes data are usually drawn from small international cohorts rather than local registries.

Delivery planning and the EXIT procedure

For tumours that compromise the airway, the ex-utero intrapartum treatment procedure has transformed survival. The fetus is partially delivered via hysterotomy while placental circulation is maintained, allowing the airway to be secured by direct laryngoscopy, bronchoscopy, or tracheostomy before complete delivery. Maternal thyroid status is relevant in this setting, and teams sometimes review maternal thyroid function given the influence of thyroid hormones on fetal lung maturity and cardiovascular stability, with further context available through resources on thyroid dysfunction in pregnancy.

Logistically, EXIT requires a deep maternal general anaesthetic to maintain uterine relaxation, a paediatric surgical team scrubbed for immediate airway or tracheostomy access, and immediate availability of neonatal intensive care. In Australian practice, planning often begins several weeks before delivery, with simulation drills and a clear chain of command. The decision about delivery mode for non-airway teratomas depends on size, vascularity, and the risk of haemorrhage, with classical caesarean section reserved for tumours that obstruct safe lower-segment access.

Postnatal management and family support

Postnatal resection is the definitive treatment for most teratomas, and the timing depends on the infant's cardiopulmonary stability and the tumour's vascularity. Neonates delivered in tertiary centres benefit from immediate access to paediatric surgical theatres, blood products, and extracorporeal support where available. Cardiac assessment with echocardiography and screening for additional anomalies is routine, and pulse oximetry screening for critical congenital heart disease is now standard practice in Australian maternity units.

Family counselling extends beyond the immediate surgical episode. Alpha-fetoprotein trends, histopathology review, and long-term surveillance for recurrence or functional sequelae form part of the follow-up pathway. Rural and remote families may need support with travel and accommodation, and Australian state-based patient-assisted travel schemes, along with charities such as Ronald McDonald House, can help reduce the financial and emotional burden of prolonged separation from home.

Practical recommendations for clinicians

• Establish a single lead clinician who coordinates imaging, intervention decisions, and family communication from diagnosis through delivery.
• Arrange fetal MRI at a tertiary centre when an airway-compromising lesion is suspected, and document airway patency assessment.
• Discuss any planned fetal intervention at a formal multidisciplinary meeting, with documentation of indications, alternatives, and maternal risks.
• Run a simulation of the EXIT procedure, including anaesthetic, surgical, and neonatal teams, before the scheduled delivery.
• Plan postnatal transfer early, and confirm bed availability, blood products, and theatre access at the receiving paediatric surgical centre.
• Provide families with written information, contact details for peer support groups, and assistance in accessing travel and accommodation schemes.

Teams across Australia are encouraged to contribute rare cases to international registries and to share de-identified imaging and outcomes at meetings such as the FAOPS and PREBIC scientific sessions. Submitting abstracts, joining working groups, and engaging with the broader perinatal community helps refine the evidence base for these uncommon but life-altering lesions. If your service manages a fetal teratoma and would like to add to the discussion, the FAOPS organising committee welcomes submissions through the official channels before the next congress.