The research offers the first scientific corroboration for anecdotes from female singers and voice professionals—who've been saying since the 1970s that childbirth affected their voices—the study's lead author, Kasia Pisanski, Ph.D., told the Washington Post.
During a 2017 concert, for example, singer Adele asked the audience to "bear with" her as she attempted to hit the low notes from her 2012 James Bond theme song, "Skyfall." "When I wrote that song, I was heavily pregnant," Adele said at the time, adding that her voice "got a lot lower" during pregnancy.
“Any other females here sound like a man when they were pregnant?" she asked. "No, just me? OK."
"Vocal masculizing"—when a woman's voice becomes lower-pitched and more monotonous—is fairly common after giving birth, researchers found. They analyzed more than 600 voice recordings of women in the public eye, including actors, broadcast journalists, and singers, divided into two groups: 20 mothers and (the control group) 20 "age-matched" women who had never given birth. The psychologists studied how the mothers' voices changed before, during, and after pregnancy over a 10-year period.
“Our results demonstrate that pregnancy has a transient and perceptually salient masculinizing effect on women’s voices,” the study authors said.
While the specific cause is still unknown, one explanation is hormone changes after childbirth, Pisanski said in a statement. "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," she said. "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."
Love it or hate it, the huskier tone is only temporary. Research indicates that women's voices typically return to their previous pitch within a year after childbirth—and at least you (hopefully!) won't have to explain that to a stadium full of fans.