An epidural is placed by an anaesthetist into the epidural space of the lower back — just outside the membrane surrounding the spinal cord — and local anaesthetic is delivered through a fine catheter that stays taped in place. It interrupts pain signals travelling from the uterus and birth canal to the brain, which is why it relieves labour pain without putting you to sleep. It is the most effective labour pain relief available and is considered safe when given with routine monitoring.
What it feels like, and why the baby is largely unaffected
The sensation is heaviness and warmth spreading down from the waist rather than complete numbness. Contractions register as pressure instead of pain, and the dose is usually reduced as pushing approaches so that you keep the sensation that guides you. Because the medicine goes into the epidural space rather than a vein, very little is absorbed into the bloodstream and very little crosses the placenta — unlike opioid pain relief given by injection, an epidural does not sedate the baby. The one indirect route to the baby is a temporary drop in the mother's blood pressure, which is why blood pressure and the baby's heart rate are both monitored after it is started. An epidural is not the same as a spinal, which is a single injection into the spinal fluid and is typically used for a planned caesarean. What an epidural actually feels like, and is it safe for the baby? covers the practical details in full.