Why do doctors recommend an IV during labor and delivery?

Hydration. Many patients aren't able to take enough fluids orally during labor because they may be nauseated and they can become dehydrated. Iv fluids can prevent dehydration. Additionally, they provide access to administer any medications that may be necessary in labor such as antibiotics or pain meds. Finally, if a cesarean section becomes necessary, the IV allows the anesthesiologist to have access.