[Newborn twins with colour difference].

A 31-year-old woman, pregnant of a monochorionic diamniotic twins had an unremarkable pregnancy. After delivery, the infants showed a colour difference. Blood analysis revealed an anaemia-polycythaemia sequence, caused by arterio-venous anastomoses in the placenta. The diagnosis was 'twin anaemia polycythaemia sequence' an acute and atypical form of twin-to-twin transfusion syndrome.