Introduction
Haemolytic disease of the foetus and newborn(HDFN) due to maternofoetal blood group incompatibility was once a significant factor in perinatal morbidity and mortality [1]. However, the widespread adoption of antenatal and postpartum use of Rh immune globulin in most western countries has resulted in a decrease in the incidence of Rh(D) alloimmunization [1, 2]. ABO incompatibility has become the most common cause of haemolytic disease of the newborn (HDN) [3].
HDN is an immune-mediated haemolytic disease, almost exclusively limited to ABO neonates with blood groups A or B delivered by women with group O. ABO-incompatible newborns with haemolytic disease are at risk for various degrees of anaemia and subsequent hyperbilirubinemia caused by immune-induced haemolysis [4]. Toxic bilirubin can occasionally cross the immature neonatal blood-brain barrier, resulting in kernicterus and subsequent life-long disabilities such as hearing impairment [5]. In a previous study, approximately one-third of ABO-incompatible newborns had significant hyperbilirubinemia and required phototherapy [6]. Phototherapy provided by modern equipment has been proven to be effective by decreasing the need for exchange transfusion (ET) in the treatment of hyperbilirubinemia [5]. However, severe subjects with dramatic haemolysis and hyperbilirubinemia, which require ET, have also been reported in clinical studies [7, 8]. In addition, the routine practice of early discharge of newborns at postnatal <48 hours lead to a higher readmission rate for hyperbilirubinemia within 14 days of birth and brings extra unnecessary expense [9, 10]. Among the identified causes of hyperbilirubinemia, ABO incompatibility was the most common [11].
ABO incompatibility cannot always be avoided, but the severity of ABO incompatibility in neonates varies greatly from region to region. Italian mothers experience a major ABO incompatibility with their newborns at a rate of approximately 11%, but haemolytic disease occurs in only 2.5% of births [12]. Both ratios are higher in Blacks, with the former farther than the latter [13]. Meanwhile other studies show that Asians have an increased likelihood of extreme neonatal hyperbilirubinemia and hospital readmission rates due to jaundice [9, 14]. However, the circumstance of ABO incompatibility remains unknown in northern China.
Our objective was to estimate the frequency of ABO incompatibility among infants, survey the incidence of haemolytic disease due to ABO incompatibility, compare the risk of haemolysis and jaundice between O-A/B and DAT-pos/neg subgroups, and assess the proportion of neonates developing ABO-incompatible haemolysis with neonatal severe hyperbilirubinemia in a single institution.