Paediatricsmiddle twist
A boy born at 38 weeks is hypotonic and feeds slowly. Rapid chromosome testing has confirmed trisomy 21. He is pink in air with a normal respiratory rate, the praecordium is quiet, no murmur is audible and the femoral pulses are easily felt. His bilirubin is well below the treatment line and he has passed meconium and urine normally. His parents ask what will be checked before he goes home. Which one of the following investigations is most important to arrange before he is discharged?