Fetal and neonatal alloimmune thrombocytopenia — structured oral station (12 minutes)

Opening prompt — "What is FNAIT, and what is the implication for this pregnancy?"

Model response, in this order: ^[1]

• "FNAIT — fetal and neonatal alloimmune thrombocytopenia — is the platelet equivalent of haemolytic disease of the fetus and newborn. Maternal IgG alloantibody against a paternally inherited fetal platelet antigen crosses the placenta and destroys fetal platelets, producing isolated fetal and neonatal thrombocytopenia. Anti-HPA-1a is the commonest antibody in people of European ancestry."^[1]
• "The implication for this pregnancy is high: recurrence is near-certain in an antigen-positive fetus, and the severity typically rises with each successive pregnancy. The feared complication is intracranial haemorrhage, which is rare but devastating."^[1]
• "The previous child had severe thrombocytopenia but no intracranial haemorrhage, which places this pregnancy in the standard-risk tier for antenatal treatment — though the risk is still significant and the treatment is mandatory."^[5]

Examiner is listening for: the platelet-equivalent framing, anti-HPA-1a as the commonest antibody, the recurrence risk, and the risk-tier classification. ^[1][5]

Probe 1 — "What antenatal management will you offer this pregnancy?"

• "Standard-risk FNAIT — a previous affected child without intracranial haemorrhage — is managed with maternal IVIG 1 g/kg per week, commenced at approximately 20 to 28 weeks' gestation, with or without low-dose prednisolone, and weekly ultrasound surveillance for intracranial haemorrhage."^[1][5]
• "The Berkowitz 2007 standard-risk randomised trial showed that early cordocentesis is not necessary for standard-risk FNAIT — IVIG protects against intracranial haemorrhage without the procedure-related fetal risk of routine early sampling."^[5]
• "I would involve the fetal medicine, haematology, neonatology and transfusion teams in a documented antenatal management plan."^[1]

Probe 2 — "How do you decide on the mode of delivery?"

• "The principle is to minimise birth trauma to a potentially severely thrombocytopenic fetus. Caesarean section is recommended for the previously affected fetus and for the fetus with a known or suspected low platelet count — commonly under 50 to 100 × 10⁹ per L for planned vaginal birth."^[1]
• "Vaginal birth may be acceptable in a selected standard-risk pregnancy once the platelet count is reassuring, with avoidance of operative vaginal delivery and fetal scalp electrodes. Operative vaginal delivery is avoided because of the bleeding risk."^[1]
• "I would plan delivery at a centre with neonatal and paediatric haematology support, with HPA-compatible or HPA-1a-negative platelets available for the neonate."^[9]

Probe 3 — "What happens to the neonate at birth?"

• "The neonatal priorities are confirm, transfuse, scan, follow up. Confirm with platelet count, anti-HPA antibody confirmation and HPA typing of the neonate."^[9]
• "Transfuse HPA-matched or HPA-1a-negative platelets for severe thrombocytopenia or bleeding. The international postnatal cohort documented a median platelet increment of 98 × 10⁹ per L with HPA-matched transfusion versus 59 × 10⁹ per L with unmatched — the matched product is preferred."^[9]
• "Perform a cranial ultrasound in every affected neonate, and arrange developmental follow-up after any intracranial haemorrhage."^[9]

Probe 4 — "What does the international evidence say about perinatal outcome?"

• "The international NOICH registry reported 615 pregnancies complicated by FNAIT, with intracranial haemorrhage in 23 fetuses or neonates (3.7%) and overall perinatal mortality of 1.1% (7 of 615)."^[1]
• "Over the registry period, management shifted from invasive procedures to non-invasive maternal IVIG treatment, and perinatal outcomes were favourable."^[1]

Communication probe — "She asks: 'Will this baby have brain damage like we were worried about last time?'"

• "I would say: your previous baby did not have a brain bleed, and that places this pregnancy in a lower-risk tier for that complication. I will treat you with IVIG through the pregnancy to raise the baby's platelet count, plan a safe mode of birth, and have the right platelets ready for the baby at birth. The international data show that with treatment, the risk of a serious brain bleed is low. I cannot promise zero risk, but the treatment we are planning is the best we have, and we will monitor closely."^[1][5]

Examiner is listening for: honest outcome framing, the standard-risk tier classification, the IVIG plan, and the availability of matched platelets. ^[1]