93987
In humans ( and perhaps in all placentals ) , the most common form is " fetomaternal microchimerism " ( also known as " fetal cell microchimerism " or " fetal chimerism " ) whereby cells from a fetus pass through the placenta and establish cell lineages within the mother .
 fetus
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 fetus