A term, ‘newborn baby’, with normal antenatal scans was referred to the transport service with severe cyanosis. There were no maternal risk factors for infection and the baby weighed 3.0 kg. The baby was born by caesarean section and after birth was noted to have ongoing cyanosis with saturations variable between 50% and 60%, although she appeared otherwise vigorous. There was mild subcostal and intercostal recession with tachypnoea. Due to the ongoing significant cyanosis despite oxygen, she was intubated and ventilated in 100% oxygen, with only marginal improvement in saturations. No murmur could be heard. The clinical examination prior to intubation is noted in Table 15.1.