A variety of other factors were not significantly associated with the odds of failed conversion: combined spinal-epidural instead of standard epidural techniques, the duration of epidural analgesia, the extent of cervical dilation at the time of epidural placement, and obesity.
However, Dr. Bauer noted, the lack of association for obesity is uncertain, given that studies varied widely in terms of when they assessed body mass index or weight relative to pregnancy. "Also, most anesthesiologists are not going to let a patient who is really obese have a nonworking epidural because we don’t want to put her to sleep" and use general anesthesia, she added.
Dr. Bauer disclosed no relevant conflicts of interest.