Background: Rhesus (Ph) incompatibility is a cause of hemolytic diseas
e of the fetus and newborn. Hemolytic disease results from the transpl
acentally transmitted maternal antibodies against Rh factor D and can
cause permanent neurological damage in the affected newborn. This stud
y examines the hypothesis that Rh incompatibility may be a risk factor
for schizophrenia. Methods: A sample of 1867 male subjects was divide
d into two groups, 535 Rh incompatible and 1332 Rh compatible, and com
pared on rate of schizophrenia. Results: The rate of schizophrenia was
significantly higher in the Rh-incompatible group (2.1%) compared wit
h the Ph-compatible group (0.8%) (P<.03). In addition, since the risk
for Ph hemolytic disease increases with second and later Rh incompatib
le pregnancies, it is noteworthy that the second- and later-born incom
patible offspring exhibited a significantly higher rate of schizophren
ia than second- and later-born compatible offspring (P<.05). Also, as
predicted, the rate of schizophrenia among firstborn incompatible subj
ects was not significantly different from that of firstborn compatible
subjects (1.1% vs 0.7%). Conclusion: Ph incompatibility may be a risk
factor for schizophrenia.