Does Epidural Analgesia in Labor Affect Fetal Heart Rates?

Anecdotally, the use of epidural analgesia for pain relief in labor seems often connected to a sudden and serious drop in fetal heart rate, often leading to panic in the delivery room and emergency cesareans. I watched this happen to my own sister. As soon as her epidural was in place, the baby's heartbeat dropped drastically, causing an immediate shift in the atmosphere of the room. First there was concern, and then worry, and finally there was "Get the OR ready, this baby needs to come out now!" She was wheeled out before any of us--including her--could wrap our heads around the situation.

Later, the doctor was very insistent that it was my sister's pelvis that was at fault. But she has no pelvic injuries, there was no indication that her pelvis was too small or too rigid to allow a baby through, and there is no family history of women being unable to get a baby through the pelvis. So she has wondered. Even knowing that correlation does not equal causation, she has still wondered. Her experience is not uncommon, as a perusal of almost any birth-related web forum will show.

According to the Mayo Clinic website, both epidural and spinal blocks have the potential to lower fetal heart rate by affecting the mother's blood pressure.¹ In and of itself, this is not necessarily a major problem. Changes in fetal heartrate do not always indicate ongoing, severe distress. Sometimes they do, however, and the combination of an actual, sustained lowering of heart rate with the potential for external fetal monitoring to give false positive results² may mean that many more women are told their babies are in danger during labor than reality would bear out. One study on the interpretation of electronic fetal heart rate monitoring does list epidural and spinal anaesthesia in it's table addressing causes of fetal brachycardia, though it is one among many.³ A 2004 study in the journal Anesthesia & Analgesia concluded that one type of epidural (cervical epidural with lidocaine) can affect the patient's heart rate.⁴ Because of the baby's connection to the mother during delivery, her state of health, particularly heart rate and blood pressure, can influence the baby's health, most particularly heart rate.

It seems there is some medical support for the idea that epidural anaesthesia, or at least some types of it may be a factor in "nonreassuring heart tones" that lead to worry in the delivery room. The connection is not altogether direct, though, so it cannot be said that an epidural will always cause these issues. It is simply one risk out of many that women must sift through as they make their choices about labor and delivery.

¹Labor and delivery: Pain medications, staff, Mayo Clinic
²Interpretation of the Electronic Fetal Heart Rate During Labor, AMIR SWEHA, M.D., TREVOR W. HACKER, M.D., JIM NUOVO, M.D., American Family Physician
³Interpretation of the Electronic Fetal Heart Rate During Labor, AMIR SWEHA, M.D., TREVOR W. HACKER, M.D., JIM NUOVO, M.D., American Family Physician
⁴The Effects of Cervical and Lumbar Epidural Anesthesia on Heart Rate Variability and Spontaneous Sequence Baroreflex Sensitivity , Makoto Tanaka , MD , Toru Goyagi , MD , Tetsu Kimura , MD and Toshiaki Nishikawa , MD, Anesthesia & Analgesia