New mothers’ voices are lower and more monotone for about a year after the birth

This article is more than 2 years old

This article is more than 2 years old

The voices of new mothers temporarily drop by more than two musical notes after pregnancy, scientists have claimed.

Researchers from the University of Sussex found new mothers’ voices become lower and more monotonous after they have had their first baby.

However, this “vocal masculinising” does not appear permanent, the team said – with voices reverting to previous frequency after one year.

They speculate the change may be an attempt to sound more authoritative in response to the new role of parent, or could be driven by hormones.

Lead researcher Dr Kasia Pisanski, of the University of Sussex’s School of Psychology, said: “Our results show that, despite some singers noticing that their voices get lower while pregnant, the big drop actually happens after they give birth.”

The study examined 20 mothers, including singers, actresses, journalists and celebrities, and compared them to a control group.

Analysis of archive interview footage in the five years before and after pregnancy found women’s mean voice pitch dropped by more than 5% – the equivalent to around 1.3 semitones.

The women’s highest pitch also dropped by an average of 2.2 semitones, or more than two notes, and they had less variation in pitch, the study found.

“Our results demonstrate that pregnancy has a transient and perceptually salient masculinising effect on women’s voices,” the authors said.

Pisanski added: “One possible explanation is that this is caused by hormone changes after childbirth.

“Previous research has shown that women’s voices can change with fertility, with pitch increasing around the time of ovulation each month, and decreasing following menopause.

“We know that after pregnancy, there’s a sharp drop in the levels of key sex hormones, and that this could influence vocal fold dynamics and vocal control.

“This effect could also be behavioural. Research has already shown that people with low-pitched voices are typically judged to be more competent, mature, and dominant, so it could be that women are modulating their own voices to sound more authoritative, faced with the new challenges of parenting.”





