Several clinical investigations on the course and outcome of pregnancies following cordocentesis have mentioned the occurrence of fetal bradycardia at the time of umbilical cord puncture. The prognostic impact of this common complication has remained controversial. Our purpose was to investigate the prevalence and the short-term and long-term consequences of fetal bradycardia associated with cordocentesis. This study included all 339 cordocenteses performed in 290 fetuses at the Division of Prenatal Diagnosis and Therapy, University of Vienna, between 1991 and 1994. Clinically significant bradycardia was defined as a drop in the heart rate to less than 100 beats/min for a period of _60 s. Bradycardia during or immediately after cordocentesis was observed in 13 cases (3โข8 per cent). The fetal/neonatal loss rate per procedure was 61โข5 per cent (8/13) in cases with bradycardia and 3โข1 per cent (10/326) in those without bradycardia (P<0โข001). Early gestational age and hydrops fetalis correlated significantly with the development of bradycardia at cordocentesis. The other risk groups, including fetuses with intrauterine growth retardation, the puncture site, and the number of puncture attempts did not correlate with fetal bradycardia. Our results indicate that prolonged fetal bradycardia during or after cordocentesis is characteristic of a group of fetuses with an especially unfavourable prognosis.