ABO hemolytic disease in Puerto Rico and North Carolina.

A prospective study was carried out at the University of Puerto Rico Hospital (UPRH) and at the North Carolina Baptist Hospital (NCBH) in order to establish the incidence of ABO hemolytic disease (ABO HD) in the two populations and to determine the relationship of intestinal parasitic infection of the mother to ABO HD in the infant. The incidence of ABO HD among UPRH at risk pregnancies (type O mother with type A or B infant) was 28.3% or 1 in 3.5 as compared with 18.4% or 1 in 5.4 of NCBH at risk pregnancies (P less than .05). Indirect Coombs' tests in cord sera, representing the passive transfer from mother to fetus of antibodies directed toward antigens on the infants' erythrocytes, were positive in 58.8% of UPRH at risk infants as opposed to 40.4% of NCBH at risk infants (P less than .001). Maternal isohemagglutinin titers at term were higher in type O UPRH mothers than in type O NCBH mothers (P less than .01). A relationship between helminth parasitic infection of the mother and ABO HD in the infant was suspected but not proved.