Effects of hypoglycaemia on fetal heart activity and umbilical artery Doppler velocity waveforms in pregnant women with insulin-dependent diabetes mellitus.

Objective: To study the effect of induced hypoglycaemia on fetal wellbeing as indicated by fetal heart rate and umbilical artery flow velocity waveforms.

Design: A prospective experimental investigation.

Setting: High risk pregnancy unit and diabetes research unit at Karolinska Institutet, Danderyd Hospital, a university affiliated hospital.

Participants: Ten women with insulin-dependent diabetes mellitus in the third trimester of pregnancy.

Interventions: The fetal heart rate, the blood flow velocity waveforms in the umbilical artery and the maternal catecholamine levels were investigated during a 150-minute hyperinsulinaemic hypoglycaemic clamp with induction and maintenance of an arterial blood glucose level of about 2.2 mmol/l.

Main Outcome Measures: 1. Fetal: changes of fetal heart rate pattern and pulsatility index of the umbilical artery flow velocity waveforms. 2. Maternal: levels of plasma adrenaline and plasma noradrenaline.

Results: Maternal hypoglycaemia was associated with an increase in frequency and amplitude of fetal heart rate accelerations, a slight decrease in the pulsatility index of the umbilical artery and a rise in the maternal catecholamine levels.

Conclusions: We speculate that the increased number of fetal heart rate accelerations reflects an increased sympathico-adrenal activity during the hypoglycaemia clamp. No potentially harmful effects on the fetus were observed in the fetal heart rate or in the umbilical artery Doppler waveform analysis during hypoglycaemia.