Post delivery uterus becomes pelvic organ by

Following delivery, the fundus lies about 13.5 cm (5 1/2") above the symphysis pubis. During the first 24 hours, the level remains constant; thereafter, there is a steady decrease in height by 1.25 cm (1/2") in 24 hours, so that by the end of the second week the uterus becomes a pelvic organ. The rate of involution thereafter slows down until by 6 weeks, the uterus becomes almost normal in sizeReference: DC Dutta&;s Textbook of Obstetrics; Chapter 13; Normal Puerperium