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OBJECTIVE: To characterize the vascular sounds of the uteroplacental blood flow obtained by microphones.METHODS: The present retrospective study took place in an anechoic chamber facility at Aalborg University, Aalborg, Denmark, in 2012, and included pregnant participants aged 18-40 years with a singleton pregnancy at 32-36 weeks and a parity of 0-2. Abdominal Doppler ultrasonography was performed bilaterally on the uterine arteries. Subsequently, in the same positions, sound recordings were performed with microphones. The derived raw sound signal was separated into two frequency ranges, and characterized accordingly.RESULTS: The mean pregnancy length among 25 participants was 33.6 ± 2.0 weeks. The pulsatility index of the uterine artery was 0.67 ± 0.24. All 50 recordings displayed the first and second maternal heart sounds (frequency 25-100 Hz), and in 17 of 50 recordings, maternal vascular murmurs (frequency 200-800 Hz) were present. The average pulse wave velocity between the maternal aortic valve and the uterine artery was estimated to be 6.6 ± 1.5 m/s.CONCLUSION: Maternal vascular murmurs in the frequency range of 200-800 Hz were identified as a possible marker of abnormal uteroplacental blood flow, and provide a means to measure the arterial pulse wave velocity.