Which Term Best Describes the Interval Between the Birth of the Newborn

Which term best describes the interval between the birth of the newborn and the return of the reproductive organs to their normal nonpregnant state?

A) Involutionary period because of what happens to the uterus
B) Lochia period because of the nature of the vaginal discharge
C) Mini-tri period because it lasts only 3 to 6 weeks
D) Puerperium, or fourth trimester of pregnancy