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

Multiparity is identified as a risk factor for placenta previa because previous pregnancies can increase the likelihood of the placenta developing abnormally in subsequent pregnancies. In women who have had multiple births, the uterine lining undergoes changes after each pregnancy, which can influence where the placenta implants. Specifically, the presence of scarring or a less favorable uterine environment in multiparous women may contribute to a higher incidence of placental abnormalities, including placenta previa.

Other factors that are recognized as risk factors for placenta previa include older maternal age, previous surgeries on the uterus, and smoking. While first pregnancy is not associated with increased risk, and low birth weight is not a direct risk factor for placenta previa, excessive weight gain post-pregnancy might affect overall pregnancy health but does not specifically increase the risk of this condition. Multiparity stands out due to its direct correlation with changes in the uterine structure and past implantation sites that can lead to placenta previa in future pregnancies.