Here are a few studies ...
I'm not sure if this is quite what you're looking for, but I had these bookmarked from my own research.The effect of epidural anesthesia on the length of labor
Epidural lengthens 2nd stage for both primiparous and multiparous women (an average of 83% and 135% longer, respectively).Adverse effects of epidural analgesia in labor
Comparison of epidural analgesia and systemic analgesia (IV narcotics) “epidural analgesia independently affected the rate of non-spontaneous delivery and the duration of the second stage of labor” “Women should be informed that prolongation of labor and increase in nonspontaneous deliveries should be expected when choosing epidural.”Choice of analgesia in labour on neonatal outcomes, delivery and maternal satisfaction with pain relief
Women laboring with an epidural “were more likely to need oxytocin augmentation to progress labour, tended to have longer time in labour and were more likely to have instrumental delivery or caesarean section than women in either the pethidine or no analgesia groups.” Babies born to mothers who had epidural analgesia had lower 1-minute Apgar scores than those whose mothers had no pain medication, but “these differences did not persist for Apgar scores at 5 minutes.”Epidural Analgesia During Labor and Delivery: Effects on the Initiation and Continuation of Effective Breastfeeding
“There was no significant difference between the epidural analgesia and no-analgesia groups in breastfeeding effectiveness or infant neurobehavioral status at 8 to 12 hours or in the proportion of mothers continuing to breastfeed at 4 weeks.”
Effect of low-dose mobile versus traditional epidural techniques on mode of delivery: a randomised controlled trial (2001) abstract full text
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“The normal vaginal delivery rate was 35.1% in the traditional epidural group, 42.7% in the low-dose combined spinal group, and 42.9% in the low-dose infusion group. These differences were accounted for by a reduction in instrumental vaginal delivery. Overall, 5 min APGAR scores of 7 or less were more frequent with low-dose technique. High-level resuscitation was more frequent in the low-dose infusion group.”Incidence of Epidural Hematoma, Infection, and Neurologic Injury in Obstetric Patients with Epidural Analgesia/Anesthesia
"The obstetric anesthesia workforce survey showed that approximately 60% of women in the United States giving birth in larger hospitals (> 1,500 births a year) have an epidural; this number decreases to 42% in smaller hospitals (100-500 births). Approximately 2.4 million women a year have an epidural for childbirth. In the United Kingdom, the epidural rate is approximately 35%; in Canada, it is 45%#; and in France in 1996, it was 51%,1 although it is difficult to obtain exact figures." The risks of specific complications in the studies they reviewed were "epidural hematoma, 1 in 168,000; deep epidural infection, 1 in 145,000; persistent neurologic injury, 1 in 240,000; and transient neurologic injury, 1 in 6,700." Smaller studies indicated somewhat higher rates.
You can also try searching for "epidural side effects" or something like that in Google Scholar
If you're looking for specific statistics in your area, hospitals often list their epidural rates on their websites; you could look those up.