Having an epidural during labour may protect key muscles and therefore cut the risk of incontinence in later life, a study of nearly 400 women suggests.
Research in the BJOG, the leading obstetrics journal, found more than one in ten women who had vaginal births suffered damage to the "levator" muscles which hold up internal organs.
A third of those who had a forceps delivery suffered some muscle trauma.
But overall women who had the spinal analgesia ran a lower risk of damage.
Injury to the pelvic muscles during childbirth is known to be a key risk factor for organ prolapse.
Women who have given birth once are four times more likely to require hospital attention because of prolapse than those who have no children, and those with two vaginal births eight times more likely.
Prolapse occurs when the pelvic muscles become so weak the organs they support - such as the bladder and the uterus - begin to drop down.
Symptoms vary, but can include sexual problems as well as both urinary and faecal incontinence - or conversely chronic constipation, depending on how the muscles are affected. There are a number of means to manage this, with surgery usually the most effective long-term option.
The team from the Nepean Clinical School of Medicine in Sydney followed up 367 women who gave birth between 2005 and 2008.
Over a third had undergone either a planned or emergency Caesarean section, and there were no cases of muscle damage or tearing among these women.
Of those who had delivered their baby vaginally, about 13% were found to have some damage.
The risk of muscle tearing was slightly lower among those whose birth had been assisted with a ventouse - a suction cup which fits on the baby's head - than those who did not have an assisted delivery.
But the use of forceps did push up the risk of damage, with a third of these births resulting in muscle injury.
The length of labour was key: a long period of pushing was strongly associated with injury.
But overall, those who had opted for an epidural, the spinal analgesia which blocks out some or all of the pain of contractions, had a lower risk of damage than those who had none.
Two-thirds of the women who suffered damage had no epidural.
The researchers, led by Dr Clara Shek, speculated there may be two reasons for this. Firstly, women who have epidurals tend to be told when to push as they can no longer feel contractions This means the potential damage from premature or over-pushing is reduced.
And physical changes in the paralysed muscle may also mean it is less likely to suffer injury.
Pain and prolapse
Epidurals are now used by about a third of women during childbirth in the UK and two-thirds in the US. They have had a mixed press in recent years, but studies show they are low risk and do not increase the need for a Caesarean section.
They have been associated with more intervention such as the use of a ventouse or forceps, although it has been noted that mothers experiencing longer and more difficult labours in the first place are more likely to request spinal pain relief.
The use of forceps, credited with dramatically reducing maternal and foetal mortality in centuries gone by, has seen a decline worldwide in recent years amid the introduction of the ventouse and safer Caesarean. In the UK, they are used in about 5% of births.
BJOG editor-in-chief, Professor Philip Steer said: "There will be occasions when the use of forceps to help deliver the baby is appropriate.
"This research shows the effects of forceps delivery are not without risk so it is important to ensure that all our trainees receive good training in carrying these out and existing doctors keep up-to-date with their skills so that levator trauma is minimised.
"Likewise, the finding that epidurals may provide a protective effect by reducing levator damage is reassuring.
"The short-term priority is to reduce pain during childbirth but the longer term effect of reducing muscle damage and prolapse is welcome."