What is the definition of the medical term "puerperium"?

A. The period of time from the beginning of labor to the birth of the baby
B. The period of time from conception to the birth of the baby
C. The period of time from the birth until the baby is discharged from the hospital
D. The first year of the infant's life
E. A six-week period after the birth in which the uterus shrinks in size