Objective— To establish a technique for continuous recording of fetal electrocardiograms (ECG) for waveform analysis in the antenatal period.

Design— Prospective descriptive study.

Setting— Fetal Medicine Unit, Queen Charlotte's and Chelsea Hospital, London, UK.

Subjects— 35 women undergoing antenatal fetal blood sampling.

Interventions— One end of an insulated Cooner wire was attached to the sampling needle and the other to an automatic ECG-ST waveform analyser.

Main outcome measures— ECG signals were obtained with the needle in the fetal abdomen during intrahepatic umbilical vein sampling or aspiration of fetal urine but not when it was in the placental cord insertion.

Results— Continuous recording of the T/QRS ratio was obtained for a total of 166 min (mean 8 min per fetus) from 20 fetuses (16–38 weeks). The T/QRS ratio had no correlation with gestational age and fetal heart rate and was similar to values described in term fetuses in labour.

Conclusions— The technique described can identify ST waveform changes and may be useful in the investigation of fetal cardiac arrhythmias, intrauterine growth retardation and in monitoring fetal transfusions.