Background and Objectives Identification of antibody characteristics and genetics underlying the development of maternal anti‐A/B linked to inducing haemolytic disease of the foetus and newborn could contribute to the development of screening methods predicting pregnancies at risk with high diagnostic accuracy. Materials and Methods We examined 73 samples from mothers to 37 newborns with haemolysis (cases) and 36 without (controls). The secretor status was determined by genotyping a single nucleotide polymorphism in FUT2, rs601338 (c.428G>A). Results We found a significant association between secretor mothers and newborns developing haemolysis (p = 0.028). However, stratifying by the newborn's blood group, the association was found only in secretor mothers to blood group B newborns (p = 0.032). In fact, only secretor mothers were found in this group. By including antibody data from a previous study, we found higher median semi‐quantitative levels of IgG1 and IgG3 among secretor mothers than non‐secretor mothers to newborns with and without haemolysis. Conclusion We found that the maternal secretor status is associated with the production of anti‐A/B, pathogenic to ABO‐incompatible newborns. We suggest that secretors experience hyper‐immunizing events more frequently than non‐secretors, leading to the production of pathogenic ABO antibodies, especially anti‐B.