Researchers from University Hospital Basel in Switzerland compared the immediate effects of brief guided imagery and relaxation exercises - two active and one passive 10-min relaxation technique - on prenatal stress in a randomized, controlled trial with 39 healthy pregnant women.

Subjects were assigned to one of two active relaxation techniques, progressive muscle relaxation (PMR) or guided imagery (GI), or a passive relaxation control condition. 

Measures were self-reported relaxation on a visual analogue scale (VAS); the State Anxiety Inventory (STAI-S); scores on the hypothalamic-pituitary-adrenal (HPA) axis (cortisol and ACTH); and sympathetic-adrenal-medullary (SAM) system activity (norepinephrine and epinephrine). Additionally, measures were taken of cardiovascular responses, such as heart rate, systolic and diastolic blood pressure.  Scores were measured at four points before and after the relaxation exercise.

 

Between groups, Progressive Muscle Relaxation and the control conditions were not as effective as Guided Imagery, which was significantly more effective in enhancing levels of relaxation.  Together with PMR, GI was associated with a significant decrease in heart rate.

Within the groups, passive as well as active relaxation procedures were associated with a decline in endocrine measures except epinephrine.

Taken together, these data indicate that different types of relaxation had differential effects on various psychological and biological stress systems. Guided imagery was especially effective in enhancing self-reported relaxation in pregnant women, while at the same time reducing heart rate.

Citation:  Urech C, Fink NS, Hoesli I, Wilhelm FH, Bitzer J, Alder J. Effects of relaxation on psychobiological wellbeing during pregnancy: A randomized controlled trial. Psychoneuroendocrinology. 2010 Apr 21. [Epub ahead of print]