Pregnancy and childbirth do come with feelings of anxiety, of course: hopes that the mother and child will be safe and healthy, that there will be little to no complications during childbirth, that the first days and months at home will go smoothly. So when do common pregnancy jitters cross the line into a clinical phobia? And, if the phobia is as prevalent as some research suggests, why isn’t it more widely recognized? The answer may have to do with the difficulty of being open about not looking forward to something that most people consider a miracle—especially when more than six million women in the U.S. alone have problems getting or staying pregnant and may dream of having children.

In the 5th century BC, the first term for a mental health condition linked to a woman's uterus was coined by Greek physician Hippocrates: hysteria. In hysteria, the uterus was thought to cause disease in many possible ways, from “moving” and blocking the health of the body to creating “female semen” that was poisonous if not removed through sexual stimulation. This “sickness” of the uterus was thought to create stress in women, all due to a lack of sexual satisfaction. Though no longer recognized, it was a diagnosis that was around for hundreds of years, whose cure was self-stimulation, manual stimulation by a doctor, or in extreme cases, institutionalization or hysterectomy. It wasn’t until 1980 that the term was removed from the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, as it was often used as a catchall for undiagnosable symptoms or those related to anxiety and similar mental health issues.

While hysteria was a diagnosis imposed on a woman in an attempt to prevent disease, tokophobia is an internal panic; it’s not the uterus itself that’s considered a danger to mental well-being, but what could happen within it—and as a result, to the rest of the body. Tokophobia is categorized in two forms: primary and secondary. The former can be understood through the lens of Mirren’s fear—often happening at a young age—when seeing disturbing images of birth or even resulting from sexual assault. The latter is often described similarly to post-traumatic stress disorder, resulting from a traumatic past birth experience.

A third form that is not recognized medically—known as social tokophobia—was conceived by Brian Salmon, a doula and lactation consultant. “Instead of it being true to secondary tokophobia, it is social—because people suck,” says Salmon. “They tell you the worst stories about their pregnancy, about their breastfeeding; all of these things.”

Salmon estimates he works with roughly 300 couples of various sexual orientations every month, and of those at least one in 10 have a severe fear of birth. “What happens is other people’s stories get ingrained in your head and anticipation of the unknown kicks in,” he says. “Then people are just so tense, they are fighting every minute and aren’t sleeping, so they show up to their birth exhausted because they are working through their early labor and just anticipating that big one that is going to come wallop them.”