Final answer:
The fundal height should be at the level of the umbilicus at 3 days postpartum for a woman who has had a vaginal delivery. This measurement indicates the uterus is contracting and returning to its pre-pregnancy size, though individual variations can occur.
Step-by-step explanation:
The fundal height at 3 days postpartum for a woman who has had a vaginal delivery should ideally be at the level of the umbilicus. Following the birth of a baby, the uterus begins to contract and reduce in size, a process called involution. By the third day after delivery, the fundal height typically descends to the level of the umbilicus, or slightly below. However, it is important to note that individual variation may occur based on factors such as multiple births, the size of the newborn, and the presence of uterine fibroids.