Subinvolution of the uterus in the postpartum period is most likely associated with which finding?

• A. Afterpains
• B. Retained placental fragments from delivery
• C. Oral temperature of 99.0ºF (37.2ºC) following delivery
• D. Increased estrogen and progesterone levels as noted on laboratory analysis

Answer: (B)

Subinvolution of the uterus happens when the uterus doesn’t return to its nonpregnant size as quickly as expected after birth. The most common reason this occurs is retained placental fragments from delivery. When bits of placental tissue remain in the uterus, they prevent complete contraction and healing of the placental site, so the uterus stays enlarged and bleeding persists longer than normal. This leads to heavier, longer lochia and a uterus that remains boggy and larger-than-expected in the early postpartum period.

Other findings listed don’t fit as tightly: afterpains are normal postpartum uterine contractions and aren’t a defining feature of subinvolution; a temperature of 99.0ºF is a mild, nonspecific finding and isn’t the hallmark of subinvolution (fever would more strongly suggest infection such as endometritis, which can be related but isn’t the canonical cause); and hormone levels drop after delivery and aren’t responsible for subinvolution.