Prevalence and lack of clinical significance of blood group incompatibility in mothers with blood type A or B.
OBJECTIVE
To examine the prevalence and clinical significance of blood group incompatibility in infants whose mothers have blood type A or B.


METHODS
We prospectively analyzed cord blood samples from 4996 consecutive love-born infants for blood type, hematocrit, and results of direct antiglobulin (Coombs) test (DAT) and indirect Coombs test (ICT).


METHODS
Erythrocyte sensitization was determined by positive DAT or ICT results. Significant hyperbilirubinemia (> or = 224 mumol/L (12.8 mg/dl) and mean cord hematocrits were compared between mother-infant pairs with ABO incompatibility and positive DAT or ICT results and those with negative Coombs test results.


RESULTS
Of all births, 6.9% (343/4996) were of infants who had ABO incompatibility and had been born to mothers with blood type B or A; 44 (13%) of 343 infants had a positive antiglobulin test result, of whom 43 had a positive ICT result only. Type A or B mothers were 5.5 times less likely to have sensitization than type O mothers; A-B, B-A, A-AB, and B-AB mother-infant pairs with a positive antiglobulin test result had mean cord hematocrits and rates of significant hyperbilirubinemia similar to those of corresponding pairs whose antiglobulin tests both showed negative results. Infants with a positive DAT result had lower mean cord hematocrits than infants with negative results on both antiglobulin tests or on a positive ICT result only. Significant hyperbilirubinemia was more frequent in infants with a positive DAT result than in infants with negative results on both antiglobulin tests or a positive ICT result only.


CONCLUSIONS
Sensitization is much rare when the mother has blood type A or B than when she has blood type O, as demonstrated by the antiglobulin test. The incidence of significant hyperbilirubinemia and lower cord hematocrit is not increased by sensitization when the mother has type A or B.
Department of Pediatrics, Magee-Women's Hospital, University of Pittsburgh School of Medicine, Pennsylvania 15213.
J A
JA
Ozolek
J F
JF
Watchko
F
F
Mimouni
D000017:ABO Blood-Group System; D001787:Blood Group Incompatibility / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology*; D001788:Blood Grouping and Crossmatching; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007567:Jaundice, Neonatal / Q000209:etiology*; D009035:Mothers; D015995:Prevalence; D011446:Prospective Studies
D000017:ABO Blood-Group System