Final answer:
The best immediate action for a pregnant client with abdominal pain and bleeding is to place her on her left side and start supplemental oxygen to maximize fetal oxygenation.
Step-by-step explanation:
A client who is 7 months pregnant presenting with abdominal pain and bright red vaginal bleeding requires immediate medical attention. Among the actions mentioned, the best and most immediate course of action is to place the client on her left side and start supplemental oxygen, as ordered. This position, known as the left lateral position, is used to maximize blood flow to the fetus and hence, maximize fetal oxygenation. It can help prevent supine hypotensive syndrome in the mother and ensures better uteroplacental perfusion. However, reassuring the client by ensuring that everything will be all right is also essential but should not replace necessary medical interventions. Administering I.V. oxytocin or massaging the fundus as immediate interventions can be inappropriate because they could potentially worsen the situation if not indicated by the underlying cause of bleeding.