It has long been speculated as to the cause of different gestation periods in mammals. Scientists have now suggested that this could be due to different placenta sizes as well as structure.

Research shows that the placenta which is vital in exchange of nutrients between mother and child and removing waste is a determining factor in the period of gestation.

Through a comprehensive analysis of 109 species of mammals, it was discovered that the gestation period decreased with the increase in complexity and degree of folds in a placenta. This was attributed to the fact that more complex and folded placentas were capable of transferring a higher amount of nutrients to the fetus, thus stimulating faster growth of the infant and reducing the period of gestation.

A case in point is the fact that mice have been found to have more complex placentas and correspondingly, a short gestation period of three weeks. On the other hand, humans and baboons seem to contain less complex placentas, and thus longer periods of gestation. The reason for this being that a lower amount of nutrients was being carried to the fetus, which results in a slower growth rate.

The study, which was published in the journal, ‘American Naturalist’, goes on to describe the complex placenta as having more interconnections and gateways for exchange of nutrients while simpler ones have a more limited connection network.

It has been previously found that larger mammals also have longer gestation periods due to their size but this new study shows that the placental structure is a force to reckon with in the determination of length of gestation.
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