In order for an infant to be considered postmature, they must be born after 42 week gestation.
In such a birth the placenta
can begin to fail, causing declining delivery of oxygen
and nutrients to the fetus
. This can result in the death of the fetus if delivery is not induced. Postmature newborns are typically thin and underweight, with slender limbs, dry wrinkled skin and longer hair and nails.
The first few days after delivery are the most critical, and infants living beyond that period have a high survival rate. A postmature child will have slightly less colored to gray eyes, as compared to a healthy newborn.
It is also known as "Ballantyne-Runge syndrome".