Women's voice pitch lowers after pregnancy

Abstract

Abstract Women's voice pitch (the perceptual correlate of fundamental frequency, F 0) varies across the menstrual cycle and lowers after menopause, and may represent a putative signal of women's fertility and reproductive age. Yet, despite dramatic changes in women's sex hormone levels and bodies during and after pregnancy, previous between-subject and case studies have not found systematic changes in F 0 due to pregnancy. Here, we tracked within-individual variation in 20 mothers' voices during their first pregnancy, as well as up to 5 years before conception and 5 years postpartum. Voice recordings from 20 age-matched nulliparous women were measured as a control. Linear Mixed Models indicated that F 0 mean, range and variation changed significantly following pregnancy in mothers, controlling for age at time of recording, whereas we did not observe any F 0 changes across corresponding timeframes in our sample of nulliparous controls. Mothers' voices became significantly lower-pitched and more monotonous during the first year postpartum compared to during pregnancy or before. These F 0 parameters did not decrease within-individuals over a 5-year period prior to conception above and beyond the effects of ageing. Although voice pitch decreased following pregnancy, mothers' F 0 parameters reverted after the first year postpartum, approaching pre-pregnancy levels. Our results demonstrate that pregnancy has a transient and perceptually salient masculinizing effect on women's voices.