FGB and familial atrioventricular septal defect: Invasive prenatal diagnosis was performed only in 7% cases (7/100; 95% CI, 2%–12%), for associated ultrasound findings ‐ structural abnormalities (non‐isolated abnormal FGB content cases, n = 3, atrioventricular septal defect, Tetralogy of Fallot, club foot, neck oedema), for twin‐to‐twin transfusion syndrome in a monochorionic‐diamniotic twin pregnancy (n = 1), two cases due to polyhydramnios and in one case for lung maturity.