Objective. To establish the clinical significance of immunohematological monitoring in reproductive-aged women. Subjects and methods. The specificity and titer of antibodies to antigens of the AB0, rhesus, and Kell systems, minor blood red cell antigens, and anti-HLA antibodies were studied in 1850 pregnancy-planning women. The role of the found antibodies was defined in the development of neonatal hemolytic disease and preterm spontaneous abortion. Results. Immune (IgG) anti-AB0 system antibodies were detected in 41.1% of the women with AB0-incompatibility with her husband. The high risk of neonatal hemolytic disease was associated with anti-A, anti-B antibody titers of 1:4 or higher. The cases of allosensitization against red blood cell antigens amounted to 5.1 and 0.86% among the rhesus-negative and rhesus-positive women, respectively. The births of babies with neonatal hemolytic disease were observed in women with anti-D, anti-DC, anti-c, anti-E, and anti-K antibodies. Conclusion. The risk of rhesus sensitization is directly related to parity and unrelated to the marital AB0 system. Anti-HLA antibodies were revealed in 0.7% of the women; moreover, there was no impact of HLA sensitization on the course and outcome of pregnancy.