Fewer tissue connections in the placenta explains the relatively long nine month gestational period in humans compared to other mammals, according to a study at Durham and Reading universities in England.
Researchers studied 109 mammal species and found that the greater interconnection between the placenta and the baby, the larger the surface to transmit nutrients from mother to baby.
“This study shows that it is not necessarily the contact with maternal blood which determines speed of growth, but the extent to which the tissues of mother and baby are ‘interlocked,’ or folded, with one another,” said lead author Dr. Isabella Capellini.
“In humans, the placenta has simple finger-like branches with a relatively limited connection between the mother’s tissues and those of the fetus, whereas in leopards, for example, it forms a complex web of interconnections that create a larger surface area for the exchange of nutrients,” she explained.
The study findings published in the journal American Naturalist conclude that the baby’s rate of development is not necessarily due to the exchange of blood between mother and fetus, but rather to the degree their tissues are interconnected.