Which of the following is a risk factor for a retained placenta?

A retained placenta can occur when the placenta is not expelled completely or effectively after childbirth. Each of the listed risk factors contributes in different ways to the likelihood of this complication.

Previous uterine curettage can lead to changes in the uterine lining or structure, potentially affecting its ability to contract and expel the placenta properly. Scar tissue formation may interfere with normal uterine wall function during the third stage of labor.

Preeclampsia is a condition that can complicate pregnancy and may impact the physiology of labor and delivery. It is associated with a heightened risk of uterine atony, which is when the uterus fails to contract adequately, leading to complications including retained placenta.

Nulliparity refers to a woman who has never given birth before. Research indicates that first-time mothers face a higher risk of various complications during labor, including retained placenta, due to the relative inexperience of the uterine muscle during the birthing process.

Given these connections, it's clear that all these factors can contribute to an increased risk of a retained placenta, making the option indicating all of the above a comprehensive choice.