Selection and characteristics of study population
311 pregnant women with RhD immunization were found eligible for
inclusion in the OPZI 2.0 study. Figure 1 shows how the study population
for the present analysis on HDFN severity in subsequent pregnancies was
selected. In total, 62 women were included, with 155 pregnancies
complicated by RhD antibodies and with a RhD-positive child (38 women
with two, 19 women with three, four women with four and one woman with
six pregnancies of RhD-positive children after her RhD antibodies were
detected). Including two twins makes a total of 157 RhD-positive
children. Table 1 shows the characteristics of included women and their
children. To assess the risk of selection bias by selecting women with
two or more subsequent pregnancies only, disease severity in the first
immunized pregnancy of patients with and without a subsequent pregnancy
was compared and showed a similar distribution (Table S1).