The topic of pelvic floor damage in childbirth is attracting more and more attention in the community. 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, it was 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. During the first vaginal birth, as many as 7 out of 10 women, will have tearing of the perineum. However, up to a quarter may have deeper, extensive vaginal trauma of the deeper muscles and supporting tissues.
The pelvic floor muscles are a supportive basin of muscle attached to the pelvic bones by connective tissue, that support the vagina, uterus, bladder and bowel. The main group of muscles providing this support is called the “levator” muscles. There are also nerves that relax or squeeze these pelvic muscles as needed.
Between the levator muscles there is an opening that allows the urethra, vagina and back passage to exit the abdomen. This is called the ‘levator hiatus’. During vaginal birth, the baby needs to pass through this opening in the pelvic floor, and the muscles, connective tissues and nerves can be damaged in the process.
To allow this to happen, the levator muscles are stretched by 1.5 to more than 3 times their normal length, depending on the type of birth. In many women, these muscles return to normal but in 25% of women the muscles are torn off the bone or overstretched. Once this trauma has occurred, the muscles and connective tissue no longer provide the support they once did. Unfortunately, it is difficult to know which women will have trauma and those that won’t.
This pelvic floor trauma is very deep and cannot be seen so is difficult to identify at the time of birth. It is often only much later when women have bladder or bowels problems, or the vaginal bulge feeling of prolapse, that the trauma is recognised. Doctors and physiotherapists who specialise in treating pelvic floor problems can detect trauma through physical examination or with the benefit of a pelvic ultrasound. A “4D” pelvic floor ultrasound by a specially trained clinician is the best method for seeing pelvic floor structures.
However, with any activity that “overloads” the pelvic floor over a long period of time e.g. straining, lifting heavy objects or coughing a lot, these pelvic floor tissues can be stretched leading to pelvic floor problems. The most common problems with loss of pelvic floor support and function are leakage of urine (urinary incontinence) and prolapse. Prolapse is when the vaginal walls (with the bladder or bowel behind) or uterus comes down to or through the entrance of the vagina and causes a bulge sensation or pressure. Some women with damage to the muscle around the back passage may have leakage of bowel contents.
Whether a woman suffers damage to the pelvic floor in labour or not depends on many things. The older a mum is at the time of the first vaginal birth, the less the tissues are able to stretch and the greater the chance of trauma. 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. Older mums-to-be may also have more difficulty getting pregnant, have more complications in pregnancy and have a higher rate of caesarean or assisted vaginal delivery e.g. forceps or vacuum.
It is also important to note that it’s the first vaginal birth that causes the most damage with the following births having less effect on the pelvic floor supports. A second vaginal birth without forceps, does not seem to cause any additional damage. However, women who have a vaginal birth after a previous caesarean section (VBAC) have higher rates of pelvic floor trauma.
The greater the size of the baby, particularly if greater than 4kg, and the longer the baby is pushed against the pelvic floor, the greater the chance of pelvic floor injury. Also, if the baby is positioned so the back is on along the mothers back (Occipito-Posterior or OP) this means the area of the head is larger causing more stretch of the pelvic floor. The biggest risk, by far, is the use of forceps. Forceps increase the amount of stretch because they increase the size coming through the pelvis and a three times greater force is applied to the pelvic floor. Forceps triple the risk of trauma to the pelvic floor muscles and anal sphincter. However, there are situations where forceps are necessary to birth the baby very quickly, which you should discuss with your maternity care team. There is also a role for episiotomy with forceps and vacuum, to reduce anal sphincter tearing.
While perineal trauma often heals well, this does not seem to occur with deeper pelvic floor tears. The problem is that with these deep ‘levator’ tears involve the muscle being torn from the bone. This tearing from the bone is called an “avulsion”. There are many studies involving hundreds of women who have been followed-up for years after a levator tear that show the muscle doesn’t reattach itself or heal. Once the muscle is pulled off the bone it shrinks and pulls back towards the back passage. 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, there is even less remaining pelvic floor support. These women can develop pelvic floor problems shortly after birth. This indicates the importance of trying to prevent the tears happening in the first place.
Do levator tears (‘avulsions’) matter? Until ultrasound could identify these tears Obstetricians and Gynaecologists were not aware that they had occurred. In fact, there are tens of thousands of women in the community who have suffered this kind of trauma in childbirth, without being aware that it had occurred. Partly this is because it takes many years of pressure on the pelvis to cause the supports to stretch to cause bladder, bowel and prolapse problems. Also, there are other parts of the pelvic floor that can compensate.
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 stretchier by about 50%
• enlarges the opening of the pelvic floor (the ‘hiatus’)
• 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 with activity e.g. coughing, sneezing and lifting, with levator trauma is much less obvious. Such urine leakage is very more common in women with or without a damaged pelvic floor, and 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 there may be a loss of feeling with sex due to vaginal laxity Others may experience pain related to the vaginal trauma and/or repair.
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 and may or may not be aware there is levator trauma. Irrespective, it is almost always worth pursuing non-surgical options, with the guidance of your treating clinician, as the first line.
What may be more of a problem is that such bodily 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. This may only become apparent in the next pregnancy. To make matters worse, there is often little post-natal care from the maternity care team in the longer term. The maternity care team is often not aware of the psychological effect of a traumatic birth, whether or not physical trauma was identified. So, for a woman and family in despair, the physical, mental and impact on their lives at large, need to be considered, assessed and care for.
Importantly, 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. Our role is to ensure women are provided all the information and support they need to make sure she is empowered to make these decisions herself without trying to persuade her otherwise.
Trauma to the pelvic floor muscle has a marked negative effect on pelvic floor structure and function and childbirth is the most significant cause of prolapse. 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, how to inform women of the risks and the options for prevention. Finally, it is vital to diagnose these severe tears to support consideration of the options, benefits and risk in terms of if, when and how to repair the damage once it has occurred.
Many physiotherapists are becoming skilled at assessing the pelvic floor for major damage, but often confirmation by imaging is needed. ABTA can provide contact information for diagnostic services.