This popular question does not have a simple answer as there are different circumstances that need to be considered.
First stage labour
There is no reason an epidural block should prolong first stage labour. To the contrary epidural can result in a shorter first stage period of labour
Pain can slow progress in first stage labour. After an epidural is administered a labouring woman is more relaxed as she no longer experiences the intense pain of contractions. Sometimes when she is pain-free and more relaxed contractions are more efficient and as a consequence there is faster progress in first stage labour than was happening before the epidural was administered.
Sometimes when contractions are inadequate for good progress in labour then is reluctance to augment labour with a Syntocinon infusion, as the labouring woman doesn’t want more painful contractions, which would be the case if the contractions were stronger and more efficient. If there is an epidural in place when contractions are suboptimal for good progress in labour, there is usually no patient objection to a Syntocinon infusion to augment labour and optimise the strength of her contractions and so her progress in labour.
When I hear stories of labours going on for days. It usually means there were either days of uterine irritability for the onset of real labour or that contractions were suboptimal and so there was suboptimal progress in labour.
Second stage labour
The onset of second stage labour is when the cervix is fully dilated. In second stage labour baby descends through the birth canal. Second stage labour is associated with this is a different pain to the contraction pains of first stage. This pressure pain causes an incredible desire for the labouring woman to ‘bear down’.
If an epidural is in place there is usually no patient awareness of second stage and no desire to bear down. So, second stage labour with an epidural can become more prolonged. Sometimes the first awareness a woman (with an epidural) has of being in second stage is when the bed sheet is raised, and the baby’s head is seen to be almost crowning.
Sometimes midwives become nervous about the duration of second stage and want to encourage the labouring woman to bear down (or ‘push’) with contractions, even though, because of the epidural, she has no desire to bear down and is not aware of the contractions. This can result in inefficient pushing and an increased the likelihood of an operative vaginal delivery because of maternal exhaustion.
If the baby’s wellbeing is satisfactory I am in no hurry for a woman with an effective epidural to start pushing once she is in second stage. I like the baby’s head to descend passively through the birth canal and for pushing to start when the baby’s head is very low in the birth canal. Such an approach increases the likelihood of a spontaneous vaginal delivery.
Yes, second stage with epidurals are often prolonged and sometimes can last two or even three hours. But this is a passive and not an active second stage and is of no risk to baby.
Sometimes Syntocinon augmentation is needed in second stage to optimise the strength of contractions and rotation and descent of baby’s head through the birth canal. Sometimes the midwife will want to ‘turn down’ the epidural so the woman gets some sensation back and so can push more effectively. Some women are reluctant to agree with this approach as they don’t want any pain. Sometimes the epidural while stopping pain doesn’t take away the sensation to bear down and so a woman can push more effectively.
So, in summary, an epidural block should not prolong first stage labour and will sometimes help reduce its duration. An epidural block will often prolong second stage labour but with careful management that usually does not mean the need for an operative vaginal delivery.