Aims: To evaluate whether maternal blood cortisol acts as an entrainer of the fetus, we compared diurnal variations in the fetal heart rate (FHR) of two cases with Cushing's syndrome, under condition of glucocorticoid replacement therapy after adrenalectomy.
Subjects: The Maternal cortisol concentration in Case 1 showed bimodal change, at 31 and 38 weeks' gestation, while the concentration in Case 2 was found to have an abnormally high level with no diurnal variation at 30 weeks and a monomodal pattern at 34 weeks.
Results: The FHR patterns in both cases demonstrated similar developmental change: a remarkable diurnal rhythm comparable to control cases was observed at 34-38 weeks. Analysis of spectral 1/f characteristics revealed, however, that Case 1 exhibited a pattern equivalent to control cases, whereas in Case 2, FHR values did not display overt diurnal variation.
Conclusions: The diurnal rhythm of FHR develops irrespective of daily variation in maternal cortisol concentration.