New mothers who eat the placenta after birth pose no harm to their newborns, contrary to a recent warning from the U.S. Centers for Disease Control and Prevention, concludes the largest-ever study of "placentophagy."

The study by researchers at Oregon State University and the University of Nevada also documented just how common the practice has become — at least among women who hold natural-is-best beliefs. About a third of 23,000 women who gave birth at home or in birth centers consumed the placenta, based on a review of their medical records, published this week in the journal Birth.

The study also found that the modern version of placentophagy is not as gross as it may sound. Almost all consumed the organ after it was dehydrated, pulverized, and put into capsules.

>>READ MORE: What you need to know about placenta encapsulation

"People are not commonly consuming it as food," said co-author Melissa Cheyney, a licensed midwife and medical anthropologist at Oregon State. "They're processing it, so they don't have to taste it."

Fans of the practice, including celebrities such as Kourtney and Kim Kardashian, claim that eating placenta turned into pills improves mood, energy, and lactation, though there is no scientific evidence to back these benefits. Preventing postpartum depression was the leading motivation cited by women in the study.

Over the last decade, social media testimonials and the rise of encapsulation technology have turned placenta pill-making into an international cottage industry, with its own associations, training courses, and certifications.

Last year, the CDC warned that downing placenta pills might put newborns at risk of dangerous bacterial infections. The alert was based on a single case of a baby in Oregon who contracted a life-threatening Group B strep infection after the mother ingested placenta pills that turned out to be infected with the same bacteria.

While it commonly lives in and on adults without causing problems, the bacteria can overwhelm newborns' immature immune systems. The CDC speculated, but couldn't be sure, that the placenta was inadequately processed to kill the pathogen and that bacteria-laden capsules increased the bacterial colony on the mother, who then transmitted the germs to the baby.

The new study looked at rates of newborn admissions to hospitals or intensive care units, as well as deaths. There were no differences between infants whose mothers did or did not eat placenta.

"Typically, you would not make health policy based on one case," Cheyney said, alluding to the CDC warning. "Our study suggests that if neonatal infection from maternal consumption of the placenta is possible, it is exceedingly rare."

She added, however, that placenta encapsulators should be careful: "You want to use safe food-handling techniques."