Sixty two samples of amniotic fluid, collected by ultrasound guided amniocentesis, were submitted to biochemical investigation including 31 samples from women with pregnancy complicated by hypertension (studied group) and 31 samples deriving from healthy pregnant women (control group with). The following parameters of acid-base balance were measured in amniotic fluids of both groups: pH, pCO2, base deficiency, standard HCO3 and total CO2. Corning device type 168 was used. Distinct metabolic-respiratory acidosis was present in amniotic fluids of studied group showing the decrease of a pH, pO2, standard HCO3 values and an increase of CO2 values and base deficiency. Authors believe in pregnancy complicated by hypertension biochemical environment of intrauterine fetal development with regard to acid-base balance is highly unfavourable.