Weight and size of the placenta in cynomolgus monkeys (Macaca fascicularis).

A gross anatomical survey of the placental development was carried out in 24 cynomolgus monkeys (Macaca fascicularis) of 4, 5, 6, 7, 8, 9, 10, 15 and 20 weeks of gestational age. Eight of the 24 placentas examined were found to be single discoidal and the remaining 16 bidiscoidal. The weight and size of placentas of each animal were measured. The average weight of the 20th week placentas was about 94 times heavier than that of the 4th week ones; the average diameter of the former was about 5 times larger than that of the latter.