Sample size calculation
Based on the literature6, 11 and an interim analysis
of our data, we expected approximately 20% of cases to be treated with
IUT, exchange transfusion or ending in foetal or neonatal death in the
first immunized pregnancy, and 45% in the second pregnancy. With a
significance of 0.05 and a power of 0.8, a total of 56 women with two
immunized pregnancies of RhD-positive foetuses would be required.