AIM: Properly describe the performance of antibody titer of immunized pregnant women, and point to the importance of monitoring pregnant women trough their gestation period to prevent hemolytic disease of newborn. METHOD: First immunohaematological testing of every pregnant woman is blood type testing in 8-10th week of pregnancy. If a pregnant woman Rhesus factor is negative, she is obligate to come on another testing in 28th and 34th week of pregnancy. For hemolytic disease of the newborn is the most characteristic finding a positive direct antiglobulin test (DAT) tested with newborn erythrocytes. This means that the newborn antibodies are coated with mother antibodies. The indirect antiglobulin test (IAT) is positive when the antibodies are found in the serum, that is, apart the fact that erythrocytes are coated by them, the antibodies are even located around the erythrocytes. Antibody titer has to be determined, too. It is clinically significant if it is 1:16. RESULTS: During my research, I’ve red another studies made on this topic, and come to conclusion that a lot of attention, past few years, has been focused on this immunization problem. People in practice work a lot to come to an idea how precisely and accurately measure antibody titer. Because of expensiveness, these methods aren’t jet in our routine work. CONCLUSION: Because of the big progress in the diagnostics, perinatal deaths caused by hemolytic disease of the newborn are reduced. In my opinion, pregnant woman have to be educated about this topic, so they could come on their testing in the right moment.