Friday, June 28, 2013

Placenta Encapsulation I: Why Would I Do That?

I haven't shared much on these pages, but I have been completing a wide-range of research for my upcoming labor and delivery. I thought I would use this space to share some of the research I've completed. This is the first post of our next Science Friday series which explores placentophagia- the act of eating the placenta after birth. While this can take several forms for humans, one of the most common is through placenta encapsulation. This post analyzes several theories that have been proposed as the cause of placentophagia.

     While nearly every mammal consumes its placenta after giving birth (a notable exception being marsupials who instead reabsorb the placenta, but do consume birth fluids), research has yet to conclusively find one overarching reason for placentophagia in mammals.  Currently, four theories are used to explain this seemingly innate mammalian behavior.  The first is that during birth, the mother, normally an herbivore, suddenly becomes carnivorous, only craving meat.  As someone who has previously given birth and has been a vegetarian for the past 12 years, I personally found this theory unlikely as I had no desire to eat meat following the birth of my first child, even when hospital’s dining facility continually ignored my vegetarian requests and primarily served me meat.  Like the rodents in studies that investigate this hypothesis, I still refused the meat!
                A second theory is that the mother simply craves food after following birth.  While any mother can attest to the fact that birth is certainly a physical feat that requires recovery, placentophagia has been observed in mammals that continue to eat throughout labor and delivery who, presumably, would not have an increase in hunger following the event.  The third theory again focuses on hunger, but this theory looks at a specific hunger for the placenta.  Research on this theory has been inconclusive as mammals that have not yet given birth will consume another animal’s placenta. 
                The final and perhaps most popular theory is that placentophagia is simply a way for mammals to maintain a clean nest in order to prevent the attraction of predators.  While this theory is straight-forward, it does ignore several refuting factors.  Firstly, as previously stated, nearly every mammal consumes its placenta.  This means that even the mightiest of predators, which are in little need to detract other mammals, takes the time to eat their placentas.  Secondly, animals who do not maintain a constant nesting site remain at the site of the birth to consume the placenta, actually putting themselves in greater risk of predators.  A final challenge to the nest theory, and the one I found most convincing, is the fact the placenta is not the only bodily expulsion during labor.  Blood and other amniotic fluids would also completely saturate the area, clearly leaving evidence of a nest, despite the removal of the placenta.  
       Each of these theories clearly has it's skeptics- check out next week's post to learn more evolutionary (and, in my mind, convincing) rationales!

Kristal, M.B. (1980). Placentophagia: A biobehavioral enigma. Neuroscience and Biohehavioral Reviews, (4)141-150.

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