Imbalance of the autonomic nervous system at night in women with gestational diabetes.

AIMS: Autonomic nervous system dysfunction is observed in Type 2 diabetes. As gestational diabetes is a potent risk factor of later Type 2 diabetes, we set out to determine whether autonomic nervous system imbalance could already be observed in women with this condition. Because activity of the sympathetic nervous system tends to be relatively stable in the nocturnal hours, we performed the study at night. RESEARCH DESIGN AND METHODS: We studied 41 women with gestational diabetes, 22 healthy pregnant controls and 14 non-pregnant controls. We assayed plasma noradrenaline at 24.00, 04.00 and 07.00 h and performed an overnight Holter recording for heart rate variability analysis. In addition, we assayed plasma adrenomedullin, a cardiovascular protective hormone.
RESULTS: Compared with non-pregnant controls, plasma noradrenaline levels were increased at 04.00 and 07.00 h in the gestational diabetic (P = 0.003) and pregnant control (P = 0.002) groups, with no difference between them. Heart rate variability, very-low-frequency and low-frequency power were lower in pregnant groups compared to the non-pregnant controls. Heart rate variability remained unchanged between specified sampling times in the gestational diabetic group, in contrast to fluctuation seen in the control groups.
CONCLUSIONS: Gestational diabetes, compared with normal pregnancy, seems not to be a state of overall sympathetic nervous system activation. At the heart level, however, an inhibitory effect on autonomic nervous system modulation was seen. Plasma noradrenaline and heart rate variability correlated well, supporting the use of this function in future studies of overall sympathetic activity during pregnancy.