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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 [SpO2], 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. [ABSTRACT FROM AUTHOR]