The ABO+ Rh blood groups and serum anti- A and anti -B anti bodies were examined in 1944 pregnant women. The results showed that 475 cases (24.4%) were positive for serum immune antibodies resulting in ABO incompatibility, and in 68 (3.4%) newborns haemolytic disease (HDN) occurred. The incidence of ABO blood group incompatibility increased with the increase of maternal serum immune antibody titer, the difference between different titers was significant (chi 2 = 4.13, P less than 0.05). Pregnant women with a high titer of serum immune antibody greater than 1:64 should be followed up regularly and those greater than 1:128 should be treated immediately. The relationship between positive serum immune antibody and blood group was discussed. We consider it is important to do maternal serum immune antibodies examination for antenatal care.