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.