The Development of Severe Neonatal Alloimmune Thrombocytopenia due to Anti-HPA-1a Antibodies Is Correlated to Maternal ABO Genotypes

Table 1

The maternal ABO type distribution in the pregnancies compared to the severity of NAIT.

Maternal ABO type	Numbers of newborns with platelet count <50 × 10^9/L (% within ABO type; 95% CI)	Numbers of newborns with platelet count 50–150 × 10^9/L	Numbers of newborns with platelet count >150 × 10^9/L	𝑃 value^†
A	34 (46.6; 0.36–0.58)	13	26	0.005
O	12 (20.0; 0.12–0.32)	14	34
B	7 (38.9; 0.20–0.61)	1	10
AB	1 (14.3; 0.03–0.51)	1	5
Total	54	29	75

Relative risk of NAIT was 0.67 (95% CI 0.48–0.94) in neonates born of women with blood group O versus blood group A.
Relative risk of severe NAIT was 0.43 (95% CI 0.25–0.75) in neonates born of women with blood group O versus blood group A.
^†Chi-square test (two-sided) for frequencies of NAIT and severe NAIT in blood group O compared to blood group A.