Comparison of unstimulated and stimulated behaviour in human fetuses with congenital abnormalities

Unstimulated (passive) and stimulated behaviour [fetal heart rate (FHR) and movements (FA)] was studied in 32 normal fetuses and 10 fetuses with conge nital abnormalities (CA). FHR and FA were recorded using a single 1.5-MHz u ltrasound transducer and analysed by computer. A 5-second vibroacoustic sti mulus (VAS) ('electronic artificial larynx') was used for the stimulation s tudies. Thus, passive and stimulated behaviour could be studied in a group of fetuses with known pathologies. One hour was used as the recording time for the passive studies and 20 min for the stimulation studies (10 min pre- and 10 min post-VAS). All CA fetuses had abnormalities of FHR and/or FA on recording passive behaviour compared to normal fetuses. However, 4 of the 10 fetuses with CA had responses to VAS that were within the normal range f or both FHR and FA. We do not feel that computerised assessment of stimulat ed behaviour in fetuses with CA confers any advantage over analysis of pass ive behaviour.