The topic of pelvic floor damage in childbirth is attracting more and more attention from non-medical people. This is not surprising – after all, a large proportion of women who have given birth naturally are affected, and so are their partners. Until recently we thought that ‘pelvic floor trauma’ meant perineal and vaginal tears, and damage to the anal sphincter, the muscle that surrounds the end of the back passage. But we now know that the muscles of the pelvic floor can also be damaged during childbirth in 15-25% of women.
The pelvic floor muscles are sometimes likened to a ‘stretched trampoline’ that runs from the tailbone (coccyx) to the pubic bone from front to back, and between the two ‘sit bones’ from side to side. In everyday life they support the organs of the pelvis (bladder, uterus, and bowel) and are able to relax and contract when needed. However, because of their position in the pelvis, they play a major role in childbirth. The muscles have to open up for the baby to pass through, and stretch by 150-600%, depending on how elastic it is, which varies a lot between people. The miracle is that in many women it doesn’t tear and even returns to normal after letting the baby through. Nobody really understands how this is possible, but we assume it has something to do with hormonal effects of pregnancy. Damage, or tearing of the pelvic floor muscles after childbirth is often not detected until much later, but over the last ten years we have become much better at how to detect tears of the muscle. Imaging techniques using magnetic resonance imaging and ultrasound, and even by just using our fingers. A 4D pelvic floor ultrasound is the best method for seeing pelvic floor structures.
In some women, even some who have never given birth the normal way, this muscle stretches a lot on pushing or just coughing. This is probably good for having babies, but it means a higher risk of prolapse of the womb, bladder and back passage. These conditions mean that someone feels a lump in the vagina that may even stick out, and there can also be bladder symptoms or problems with the back passage.
Whether someone suffers damage to this muscle in labour or not seems to depend on many things. The older a mum is at the time of the first vaginal birth, the higher the risk of major damage. That’s very important. People should know about this when they think about having kids. The longer one waits with having children, the lower the likelihood of falling pregnant without help, and the higher the risk of needing a Caesarean or Vacuum or Forceps. And even if a woman manages to avoid a Caesarean, the risk of pelvic floor muscle trauma rises by about 10% with every year of delay in having your first child.
Incidentally, it’s the first baby that matters the most. Whether someone has one child born the normal way or three doesn’t seem to make much of a difference to the pelvic floor. A second baby does not seem to cause any additional damage- unless the first was born by Caesarean, and the second the normal way (vaginal birth after Caesarean, VBAC).
The more difficult a vaginal delivery, the higher the risk of pelvic floor injury, and other factors such as a long labour, OP presentation (when the baby faces upwards rather than downwards) and a big baby probably increase the risk as well. The main problem however is the use of forceps for delivery. There are studies from all over the world showing that it triples the risk of pelvic floor muscle tears. An Epidural seems to protect the pelvic floor to some degree.
Some childbirth-related damage, such as small perineal tears, are often not repaired because we think they’ll heal well by themselves. So, do those pelvic floor muscle tears heal? We have now followed up hundreds of women after their first birth, and there seems to be very little change over time. Once the muscle is pulled off the bone it shrinks and pulls back towards the back passage (it ‘retracts’), and there is no way it can move back to where it came from. In some women the tears are not complete, and scar tissue can bridge a partial tear, but once the muscle is completely off the bone, the defect probably won’t heal. In some women this happens on both sides, making matters worse.
Do defects of the pelvic floor muscle (‘avulsions’) matter? After all, Obstetricians and Gynaecologists seem to have completely missed them until now! In fact, there are many thousands of women in the community who have suffered this kind of trauma in childbirth, without noticing any problems. Partly this may be because such problems sometimes take a long time to develop, but in others those parts of the pelvic floor muscle that are higher up (mainly the iliococcygeus muscle) can compensate and take most of the load of the pelvic organs.
What we can say right now is that pelvic floor muscle trauma (‘avulsion’):
weakens the muscle by about 1/3 on average
makes the muscle more stretchy by about 50%
enlarges the opening of the pelvic floor (the ‘hiatus’) by about 1/4
more than doubles the risk of bladder prolapse
triples the risk of prolapse of the uterus (the womb)
triples the risk of a prolapse returning after pelvic floor surgery.
The link with loss of urine on coughing, sneezing etc (something people often blame on a ‘weak pelvic floor’) is much less obvious. Urine leakage is a little more common in women with a damaged pelvic floor, but there are many other factors involved (see incontinence link). And then there is another question: how much does over- stretching or tearing of this muscle affect sexual function? In some women the site of the tear is tender, even after decades, and sometimes the intact muscle opposite an avulsion can get spastic and painful.
Some women and their partners notice a big difference after the birth of their first child. Others don’t notice anything. On average, women feel that there is more laxity and less muscle strength in the vagina, and sometimes that makes them seek help from gynaecologists who end up suggesting some kind of vaginal surgery, unaware of what the real problem is.
What may be more of a problem is that such changes remind women of what happened during the delivery, and sometimes the experience is so traumatic that it can lead to postnatal depression or even post-traumatic stress disorder. Neither doctors nor midwives have been aware that often there is real, major damage to account for someone’s despair- it’s often not just in the mind. Treating only the mind while ignoring what’s happened to a woman’s body may not be very effective. And if someone knows a mother who has suffered major trauma (to the body or mind) during the delivery of her baby, and decides to have her first baby by Caesarean then we should take such concerns seriously (tocophobia) and let her make those decisions herself without trying to persuade her otherwise.
What are we going to do about this?
Trauma to the pelvic floor muscle has a marked negative effect on pelvic floor structure and function. It’s probably responsible for many (if not most) cases of prolapse of the womb and bladder. As we are becoming more aware of the problems and issues around pelvic floor trauma, there is a growing body of research looking into determining the most effective means of predicting those women most likely to suffer from this type of trauma, and how to repair the damage once it has occurred.