Which of the following is a risk factor for uterine atony?

Multiple gestation is recognized as a significant risk factor for uterine atony, which is the failure of the uterus to contract effectively after childbirth. In cases of multiple gestation, the uterus is typically over-distended due to the presence of more than one fetus. This over-distension can lead to alterations in the uterine muscle fibers and contribute to a decreased ability to contract effectively, increasing the risk of atony and subsequent postpartum hemorrhage.

The risk is compounded by the fact that with multiple gestations, there is often a larger volume of placental tissue and associated vascular structures that need to be managed after delivery. This increases the demand for effective uterine contraction to ensure that bleeding is adequately controlled post-delivery. Hence, multiple gestation is a critical factor to consider when assessing the likelihood of uterine atony.

Advanced maternal age, prior cesarean section, and low birth weight may have some association with uterine contractility issues, but they are less directly linked to the risk of atony compared to the implications of multiple gestation.