What is the medical term meaning expiring placenta?

An expired/expiring placenta is when hormonal trigger tell the placenta that its done its duty and it's time to go. Usually it doesn't happen until after 40 weeks. If it happens early, as it does many times with multiple births, then the babies could be born prematurely or they could have late gestational failure to thrive because of the lack of nutrients. If oxygen delivery is also affected, cerebral palsy could result.