Final answer:
The most appropriate intervention to slow postpartum bleeding after ensuring no additional fetuses are present would be to mix 10 units of oxytocin with lactated Ringer's solution, stimulating uterine contractions to aid in reducing hemorrhage.
Step-by-step explanation:
After attempting to slow the bleeding associated with natural childbirth by non-invasive means and ensuring there is not a second fetus present, the most appropriate intervention for the new mother would be C) Mix 10 units of oxytocin to 1 liter of lactated Ringer's solution and run at 20-30 gtts/min. This administration of oxytocin stimulates uterine contractions, helping to control postpartum hemorrhage by aiding the process of involution, where the uterus contracts to return to its pre-pregnancy size. This also helps the expelled placenta and fetal membranes to be more thoroughly evaluated to ensure completeness, and reduces the risk of bleeding caused by retained fragments.
Making sure the placenta is intact and without retained fragments is crucial because these can cause significant bleeding. Additionally, frequent breastfeeding supports the process of involution as well since it facilitates the release of natural oxytocin which aids in uterine contractions.