Some eat it raw, others cook it. Some make it into jerky, and others grind the cooked, dried remains into a brown powder and fill capsules.

However it's done, eating the placenta after childbirth is thought to ward off postpartum depression and boost milk production, among other things. There is no solid scientific evidence backing these benefits, though, and cooking it reduces the nutritional content. Nevertheless, the practice of eating the fetus-nourishing organ has strayed from the fringe in recent years, with celebrities such as January Jones and Kim Kardashian joining in. In a December 2015 blog post, Kardashian went through her thought process, noting anecdotes of other women who had good experiences. "So,” she wrote, “I thought, why not try it? What do I have to lose?"

As it turns out, the answer is the health of your newborn, according to the Centers for Disease Control and Prevention. In a new case report published in the agency’s Morbidity and Mortality Weekly Report, researchers caution against the practice, noting that the commercial and at-home preparation methods could leave your DIY organ supplements contaminated with infectious pathogens.

At least that was the case for one Oregon mother. In September of 2016, the healthy woman, who gave birth to a healthy baby after an uncomplicated pregnancy, watched (likely in horror) as her newborn’s health quickly deteriorated. Shortly after birth, the baby showed signs of respiratory distress, was admitted to the neonatal intensive care unit, and was found to have a life-threatening blood infection—diagnosed as late-onset group B Streptococcus agalactiae (GBS) bacteremia. After an 11-day course of antibiotics in the hospital, the baby improved and went home.

A dangerous dose

But not five days later, the baby arrived in another hospital, again with a GBS infection. Puzzled as to why the infection recurred, the doctors there started asking questions and found that the mother was taking placenta pills. She had hired a company—which the researchers only identify as “Company A”—to make pills for her. The company notes on its website that it cleans, slices, and dehydrates placentas at 115°F–160°F (46°C–71°C), then grinds and places them into about 115–200 gelatin capsules, stored at room temperature.

The researchers note that this process may not heat the organ to a high enough temperature or for long enough to reduce pathogens. For instance, when cooking meat at just 130°F, it takes around two hours to kill off Salmonella.

When the researchers examined the pills, they found that they were packed with not just placenta powder but GBS as well. Using whole genome sequencing at CDC labs, researchers found that the GBS strains in the pills were genetically indistinguishable from the GBS infecting the baby.

GBS is commonly found in and on adults, but it usually doesn’t cause infections. In newborns with undeveloped immune responses, however, it can wreak havoc. And the strain of GBS found in this case was particularly nasty; it had virulence factors that allowed it to easily slip through the intestinal lining and into the bloodstream—and potentially cross the blood-brain barrier.

The doctors speculate that ingesting the bacteria-crammed capsules elevated the GBS levels in the mother’s intestines and/or on her skin. And those bolstered bacteria were then able to transfer to the baby.

“The placenta encapsulation process does not per se eradicate infectious pathogens; thus, placenta capsule ingestion should be avoided,” the researchers conclude. “Clinicians should inquire about a history of placenta ingestion in cases of late-onset GBS infection and educate mothers interested in placenta encapsulation about the potential risks.”