More than 200 millennia of human civilization and two centuries of modern medicine have brought us to this recent heavy-handed admonition by scientific researchers:

It’s probably a bad idea to eat your placenta.

The 11-page, medical jargon-filled article published this month in the American Journal of Obstetrics & Gynecology seeks to provide a clear answer to what many view as a somewhat gross question.

Over the past decade, the authors say, there’s been a growing interest in natural childbirth by people wary of bringing a human life into the world in an antiseptic room full of intravenous drugs, gloved doctors and fluorescent light. And many have questioned whether doctors have it all wrong when they place a placenta in a biohazard bag and toss it out.

After all, for many mammals, the consumption of placentas — placentophagy, as researchers call it — has been going on for as long as there have been placentas.

But the recent article seeks to tackle two major questions: Is the practice beneficial? And is it safe?

For anyone who missed that day in biology class, the placenta is an organ shared by a pregnant mother and her growing fetus, functioning as the lungs, gastrointestinal system, liver and kidneys of the developing child.

During birth, the organ is expelled along with the baby, and most hospitals discard it as medical waste.

Proponents have said eating placenta reduces pain, improves mood and energy level, increases milk production, and may even have anti-aging properties — a wonder drug produced by a pregnant woman’s own body.

For humans, eating placenta has been a fringe practice until recently.

Positive placenta-eating anecdotes have flourished, and so have companies that charge hundreds to prepare a placenta for consumption, dehydrated like beef jerky or processed into smoothies or pills.

Meanwhile doctors — and policymakers who regulate what is safe to put in our mouths — admit to being somewhat flummoxed by the practice.

According to the research paper, more than half of obstetricians and gynecologists said they were uninformed about the risks and benefits of the practice, and 60 percent said they weren’t sure whether they should be in favor of it.

That vacuum of sound medical advice from family doctors has been filled by celebrities and reality TV stars.

January Jones told People magazine that placenta consumption is “not witch-crafty” and that the capsules helped her get back to a grueling “Mad Men” shooting schedule after her son was born. She ingested the placenta pills every day.

“Your placenta gets dehydrated and made into vitamins,” she told the magazine. “It’s something I was very hesitant about, but we’re the only mammals who don’t ingest our own placentas.”

Kim Kardashian West tweeted about eating her placenta in a bid to get people to download her app. Her sister, Kourtney, pretended to feed some placenta to her family as a prank.

Buoyed by the celebrity endorsements, a cottage industry has sprung up to make placenta palatable — more like popping a vitamin pill and less like the Dothraki pregnancy ceremony from “Game of Thrones.

So there’s no question that people are eating placentas, but is anything good happening afterward?

The researchers’ answer: Nope.

They acknowledge the claims made by proponents, but analyzed any scientific studies they could get their hands on — and found them lacking. Many were unscientific or surveys taken by people who’ve self-selected to participate, raising serious questions about bias. The researchers warned that positive anecdotes about improved emotions may be influenced by the placebo effect.

Until recently, it’s been of little consequence. People have always done things that seem weird or gross to others — unpalatable but harmless.

But in June the Centers for Disease Control and Prevention released a warning about placenta eating. A new mom in Oregon passed on a potentially deadly blood infection to her breast-feeding baby, as The Washington Post’s Peter Holley reported. The cause: capsules of the placenta the mother had been ingesting since giving birth.

“Because placentophagy is potentially harmful with no documented benefit, counseling women should be directive: physicians should discourage this practice,” the recent study says. “Health care organizations should develop clear clinical guidelines to implement a scientific and professional approach to human placentophagy.”

The study also sought to debunk the claims made by ardent proponents of placenta ingestion.

The organ does contain small amounts of Oxytocin, a drug that causes “the smooth muscles around the mammary cells to contract and eject milk,” the study says, but there’s no indication that Oxytocin or other hormones can be absorbed from eating a placenta. In rats, placenta ingestion was found to increase the pain threshold “without inhibiting the ability to care for the offspring,” but a similar effect in humans has not been found.

Still, changing made-up minds may be difficult.

The doctors on the study have PhDs, yes, but they don't have the reach of a reality television show or an app like Kardashian West, who gushed about eating her placenta.

“I can’t go wrong with taking a pill made of my own hormones — made by me, for me. I started researching and read about so many moms who felt this same way and said the overall healing process was so much easier.”

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