The investigation has been conducted with the aim of studying association between polymorphic marker G1846A of CYP2D6 gene and efficacy and safety of bisoprolol in 64 pregnant women with chronic stage I and II hypertension. These women have been under observation during trimesters II and III of pregnancy. Results of the study evidence for the absence of differences in frequencies of alleles and genotypes of polymorphic marker CYP2D6 of CYP2D6 gene between groups with various regimens of antihypertensive therapy. An important conclusion has been formulated that in pregnant women with chronic arterial hypertension receiving antihypertensive therapy with bisoprolol and nifedipine polymorphic marker CYP2D6 of CYP2D6 gene is not associated with prognostically unfavorable hemodynamic changes in maternal-placental-fetal-compartment - altered parameters of dopplerometry of maternal-placental blood flow and cardioflowgraphy.