Final answer:
Following vaginal birth in a woman with marginal placenta previa, the greatest risk is hemorrhage. This is due to the potential for remaining placental fragments and ineffective contraction of the uterus, both of which can lead to excessive postpartum bleeding.
Step-by-step explanation:
A woman diagnosed with marginal placenta previa has recently given birth vaginally. Following childbirth, during the postpartum period, she is at the greatest risk for hemorrhage, especially with a condition like placenta previa. A woman with marginal placenta previa is at increased risk of antepartum hemorrhage during pregnancy due to the placenta partly covering the cervical opening, which can also lead to a higher risk of postpartum hemorrhage because of the increased likelihood of placental fragments remaining in the uterus or due to ineffective uterine contraction.
Even after the placenta is expelled, the uterine contractions must continue to help reduce blood loss from the site where the placenta detached. If the placenta or its fragments do not get expelled completely, or if the contractions are not strong enough to compress the blood vessels, this scenario can result in excessive postpartum bleeding, which is why hemorrhage is a significant concern after a vaginal birth following a marginal placenta previa diagnosis. Other postpartum issues such as infection, urinary retention, and thrombophlebitis are also potential complications, but the immediate and greatest risk is typically hemorrhage.