Placentophagy

Placentophagy (from 'placenta' + Greek φαγειν, to eat; also referred to as placentophagia) is the act of mammals eating the placenta of their young after childbirth. It's also cropped up among a very small number of particularly nutty circles as a form of alternative medicine. There's also just about no record of the practice ever existing historically in any form other than modern Age of Aquarius woo. Even in the placentophagy tests that have been performed, there isn't any evidence that animals prefer eating the placenta to eating liver given to them by scientists as an alternative. A 2015 review of placentophagy found no evidence of benefit, and there is a risk of consuming bacteria and viruses, particularly if the placenta is not your own.

Eating a favorite meat dish after giving birth probably has the same benefits, such as they are, as placentophagy. The hippie-era Birth Book by Raven Lang (1972) has a lovely recipe for placenta with some fava beans and a nice chianti.

China
In traditional Chinese medicine, human placenta has been used: For anemia and emaciation. For general weakness in women, and black spots on the face. For all kinds of weakness in both sexes, for delirium and convulsions, and loss of will power. To quieten the heart, benefit the respiration and as a seminal tonic. For conjunctivitis and growth over the eyes.

A liquified placenta that has been buried for several years, sometimes with other drugs, has been used: For head-scabs in children, fevers, ceaseless attack of feverish chills, delirium. Given to quieten a patient whose hair stands up without cause. For constipation. To cure infectious diseases.

Dangers
Since a human placenta is dead human flesh, any bacteria that grow on it will be the bacteria that devour human flesh; there is a reason we have an instinctual aversion to "recycling".

In 2017, it was reported that an Oregon woman gave her placenta to a dehydrating company that returned to her the desiccated placenta in capsules for her to eat. After eating the capsules, the woman passed along a Streptococcus agalactiae infection to her baby, which was also present in the capsules.

A 2017 review in the American Journal of Obstetrics & Gynecology found that any benefits of placentophagy was limited to anecdotal evidence, that there was no scientific evidence of benefit, and that due to the aforementioned risk of passing infection on to the baby, mothers should be discouraged from the practice by physicians.