I have done a brief search, and found this article about the cascade of intervention:
"Epidural analgesia can provide very effective pain relief during labor. It also increases the risk of experiencing a sudden drop in blood pressure, a longer labor, difficulty moving about, difficulty urinating, difficulty pushing the baby out, fever, and other undesirable effects.
A variety of interventions — such as continuous electronic fetal monitoring and intravenous fluids — are widely used with epidurals to monitor, prevent or treat these effects. And others become more likely, including use of synthetic oxytocin to strengthen contractions, use of a urinary catheter to empty the bladder, and use of a vacuum extractor or forceps to help move the baby out. These in turn may have side effects that lead to the use of other interventions.
The impacts can also extend to babies. For example, epidurals increase a woman’s likelihood of developing a fever; if a mother has a fever, caregivers worry that her baby may have an infection. Though few babies whose mothers have an epidural associated fever do in fact have an infection, as a precaution these babies often have blood tests and are treated with antibiotics just after birth. They may also be observed in a special nursery, which can interfere with bonding and breastfeeding."
This Australian article states that nearly 50% of women who have epidurals go on to have an instrumental or operative delivery. That has to be higher than the number of instrumental deliveries following on from other forms of analgesia, surely? It also increases your risk of having a C-section by 160%, and is linked to longer labours, according to this article.