The Effect of Nonstress Device Noise Level on Stress Parameters in Primigravid Women: A Randomized Controlled Trial.

Introduction: This study evaluated the effect of the noise level of the nonstress test (NST) device on stress parameters in primigravid women.

Methods: A total of 44 pregnant women participated in a randomized clinical trial between February and October, 2021. The participants were divided randomly into 4 equal groups using an automated web-based randomization system and ensuring allocation concealment: the control group (NST device volume turned off), intervention group I (1-35 dB(A)), intervention group II (36-60 dB(A)), and intervention group III (61 dB(A) and above). A data collection form was used to record personal information and stress parameters. Stress parameters (blood pressure, heart rate, oxygen saturation [SpO], blood glucose, salivary cortisol, and salivary adrenocorticotropic hormone [ACTH]) levels were measured pretest (0-2 minutes before NST starts), midtest (at 10 minutes of the NST), and posttest (within 0-2 minutes after NST was finished). The study was registered at ClinicalTrials.gov (identifier: NCT05488704).

Results: NST sound levels above 35 dB(A) increased the average cortisol and ACTH levels in the posttest. NST sound levels were positively correlated with posttest cortisol (r = .448) and posttest glucose (r = .302). There was interaction effect on heart rate, glucose, and cortisol level by time, indicating that the intervention groups experienced a significant acceleration in heart rate, glucose, and cortisol level after a noise intervention compared with the control group.

Discussion: Midwives should continue applying NST below 36 dB(A), considering the factors that may induce stress during the NST process.