Many factors determine when you can get an epidural, including the position of the baby in the birth canal, or whether this is your first baby or a later child. Some obstetricians/midwives would prefer that you be dilated at least four centimeters prior to getting an epidural. These obstetricians/midwives believe that an early epidural may slow your labor, but the available data on this topic is controversial. Certain medical conditions, however, may favor earlier commencement of epidural analgesia. Once the obstetrician/midwife gives his/her permission for you to get an epidural anesthetic, the anesthesiologist will place the epidural. If you have not seen an anesthesiologist in advance, an abbreviated history and physical, and consent for the procedure will be obtained. 

Various studies report conflicting data with regard to the level of risk of cesarean delivery for nulliparous women (women with first pregnancy) who receive epidural analgesia before 5 cm of cervical dilatation. As a result some institutions are requiring that laboring women reach 4-5 cm of dilatation before receiving epidural analgesia. It is unclear whether these institutions have developed local protocols that are sensitive to patients' needs. Labor results in severe pain for many women, and there is no other circumstance where it is considered acceptable for a person to experience untreated severe pain, amenable to safe intervention.  Therefore , the American College of Obstetricians and Gynecologists wishes to reaffirm the opinion published jointly with the American Society of Anesthesiologists that while under a physician's care, in the absence of medical contraindication, maternal request is sufficient medical indication for pain relief during labor. Decisions regarding analgesia should be coordinated among the obstetricians, the anesthesiologist, the patient, and support personnel. 

For a recent update on this subject that generated considerable public interest --  Click here