The Anterior Cervical Lip: how to ruin a perfectly good birth
Here is a scenario I keep hearing over and over: A woman is labouring away and all is good. She begins to push with contractions, and her midwife encourages her to follow her body. After a little while the midwife checks to ‘see what is happening’ and finds an anterior cervical lip. The woman is told to stop pushing because she is not fully dilated and will damage herself. Her body is lying to her – she is not ready to push. The woman becomes confused and frightened. She is unable to stop pushing and fights her body creating more pain. Because she is unable to stop pushing she may be advised to have an epidural. An epidural is inserted along with all the accompanying machines and monitoring. Later, another vaginal examination finds that the cervix has fully dilated and now she is coached to push. The end of the story is usually an instrumental birth (ventouse or forceps) for an epidural related problem – fetal distress caused by directed pushing; ‘failure to progress’; baby mal-positioned due to supine position and reduced pelvic tone. The message the woman takes from her birth is that her body failed her, when in fact it was the midwife/system that failed her. Before anyone gets defensive – I am not pointing fingers or blaming individuals, because I have been that midwife. Like most midwives I was taught that women must not push until the cervix has fully dilated. This assumption has been taught to midwives since the 1930s and Ina May herself warned against ‘early pushing’ in Spiritual Midwifery. This post is an attempt to prompt some re-thinking about this issue, or rather this non-issue.
Anatomy and Physiology
Birth is an extremely complex physiological process but very simplistically 3 main things occur:
- Dilatation of the cervix
- Rotation of the baby through the pelvis
- Descent of the baby through the pelvis
But this is not a step-by-step process – it’s all happening at the same time, and at different rates. So whilst the cervix is dilating the baby is also rotating and descending.
1. Dilatation of the cervix
The cervix does not open as depicted in obstetric dilatation models ie. in a nice neat circle (Sutton 2001). It opens from the back to the front like an ellipse. The ‘os’ (opening) is found tucked at the back of the vagina in early labour and opens forward. At some point in labour almost every woman will have an anterior lip because this is the last part of the cervix to be pulled up over the baby’s head. Whether this lip is detected depends on whether/when a vaginal examination is performed. A posterior lip is almost unheard of because this part of the cervix disappears first. Or rather it becomes difficult to reach with fingers first.
The cervix dilates because the muscle fibres in the fundus (top of the uterus) retract and shorten with contractions = pull it open (Coad 2011). This does not require the pressure of a presenting part ie. baby’s head or bottom (lets stick to heads for now). However, the head can influence the shape of the cervix as it dilates up around it. For example, a well flexed OA baby (see pic A) will create a neater, more circular cervix. An OP and/or deflexed baby (see pic B) will create a less even shape. For more about OA and OP positions see this post. Most baby’s will be somewhere between these two extremes whilst the cervix is opening and will be changing their position as they rotate.
Babies enter the pelvis through the brim. As you can see from the pictures above this is easier with their head in a transverse position. As the baby descends into the cavity their head will be tilted – with the parietal bone/side of the head leading. This is because the angle of the pelvis requires the baby to enter at an angle – see picture on the right. Once in the cavity the baby has room to rotate into a good position for the outlet which is usually OA. Rotation is aided by the pelvic floor and often by pushing.
3. Descent – the urge to push
The urge to push… and I’m talking spontaneous, gutteral, unstoppable pushing… is triggered when the presenting part descends into the vagina and applies pressure to the rectum and pelvic floor. This is sometimes called the ‘Ferguson reflex’ – probably after some man. This reflex is not dependent on what the cervix is doing, but where and what the baby’s head is doing. So, if the baby’s head hits the right spot before the cervix has finished dilating the woman will spontaneously start pushing. An alternative but common scenario is when the cervix is fully open but the baby has not descended far enough to trigger pushing. Unfortunately some practitioners will tell the woman to push and create problems instead of waiting for descent and spontaneous pushing.
Pushing before full dilatation
Because we are not telling women when to push (are we?!) they will push when their body needs to. If we are directing pushing we risk working against the physiology of birth and creating problems (see previous post). There is very little research about pushing before full dilatation. Downe et al. (2008) report research conducted in the UK in 1999, and recently Borrelli, Locatelli & Nespoli (2013) published a small observational study. These studies found that the incidence of ‘early pushing urge’ EPU (as it is referred to in the literature) is between 20% to 40%. Interesting Borrelli et al. (2013) found that the sooner the midwife performed a vaginal examination in response to a woman’s pushing urges, the more likely they were to find the cervix still there. They also found that ‘early pushing’ was much more common with primips (first labours)… perhaps because they are likely to take longer pushing, therefore be more likely to have a vaginal examination? And early pushing occurred in 41% of women with OP babies.
Spontaneous pushing before full dilatation is a normal and physiologically helpful when:
- Baby’s head descends into the vagina before the cervix has dilated. In this case the additional downward pushing pressure assists the baby to move beyond the cervix.
- Baby is in an OP position and the hard prominent occiput (back of head) presses on the rectum. In an OA position this part of the head is against the symphysis pubis and the baby has to descend deeper before pressure on the rectum occurs from the front of the head. In the case of an OP position, pushing can assist rotation into an OA position.
I am yet to find any evidence that pushing on an unopened cervix will cause damage. I have been told many times that it will, but have never actually seen it happen. Borrelli et al. (2013) found no cervical lacerations, 3rd degree tears, postpartum haemorrhages in the women with an EPU. I have encountered swollen oedematous cervixes – mostly in women with epidurals who are unable to move about. But, this occurs without any pushing. I can understand how directed, strong pushing could bruise a cervix. But I don’t see how a woman could damage herself by following her urges. In many ways the argument regarding pushing, or not is pointless because once the Ferguson reflex takes over it is beyond anyone’s control. You either let it happen, or start commanding the women to do something she is unable to do ie. stop pushing.
Telling women to push or not to push is cultural, it is not based on physiology or research. For example, in some parts of the world eg. Central Africa, women are told to push throughout their entire labour (on an unopened cervix!). This is often accompanied by their midwife manually stretching the cervix too – ouch. Alternatively, in other parts of the world eg. the US women are told not to push until a prescribed point in labour. It seems midwives are bossy worldwide.
When left to get on with their birth, occasionally women will complain of pain associated with a cervical lip being ‘nipped’ between the baby’s head and their symphysis pubis during a pushing contraction. In this case the woman can be assisted to get into a position that will take the pressure off the cervical lip (eg. backward leaning). When undisturbed women will usually do this instinctively. At a recent waterbirth a mother (first baby) who had been spontaneously pushing for a while on all fours floated onto her back. A little while later she asked me to feel where the baby was (for her not me) – baby was not far away with a fat squishy anterior lip in front of the head. The mother also had a feel, then carried on pushing as before. Her daughter was born around 30 mins later.
Avoid vaginal examinations (VEs) in labour. What you don’t know (that there is a cervical lip) can’t hurt you or anyone else. VE’s are an unreliable method of assessing progress, and the timelines prescribed for labour are not evidence based (see this post).
Ignore pushing and don’t say the words ‘push’ or ‘pushing’ during a birth. Asking questions or giving directions interferes with the woman’s instincts. For example, asking ‘are you pushing’ can result in the women thinking… am I? Should I be? Shouldn’t I be? Thinking and worrying is counterproductive to oxytocin release and therefore birth. If she is pushing, let her get on with it and shush. For more about pushing in general and a link to a great audio by Gloria Lemay see this post.
Do not tell the woman to stop pushing. If she is spontaneously pushing (and you have not coached her) she will be unable to stop. It is like telling someone not to blink. Pushing will help not hinder the birth. Telling her not to push is disempowering and implies her body is ‘wrong’. In addition, after fighting against her urge to push she may then find it difficult to follow her body and push when permitted to do so (Bergstrom 1997).
If a woman has been spontaneously pushing for a while with excessive pain (usually above the pubic bone) she may have a cervical lip which is being nipped against the symphysis pubis. There is no need to do a vaginal examination to confirm this unless she wants you to. If you suspect, or know there may be a cervical lip:
- Reassure her that she has made fantastic progress and only has little way to go.
- Ask her to allow her body to do what it needs to, but not to force her pushing.
- Help her to get into a position that takes the pressure off the lip and feels most comfortable – usually a reclining position. She may be in a forward leaning position because it relieves the back pain associated with an OP presentation and be reluctant to move. This is one of the rare times a suggestion/direction is appropriate.
- If the situation continues, and is causing distress – during a contraction apply upward pressure (sustained and firm) just above the pubic bone in an attempt to ‘lift’ the cervix up.
- If the woman is requesting further assistance, the cervical lip can be manually pushed over the baby’s head internally – by her or you. This is extremely uncomfortable! Be aware that this may allow the baby’s head to move into the vagina before he/she has rotated which could create further problems.
Note: This nipping situation is rare and usually a cervical lip will simply move out of the way without causing any problems.
An anterior cervical lip is a normal part of the birth process. It does not require management and is best left undetected. The complications associated with a cervical lip are caused by identifying it, and managing the situation as though it is a problem.
This post is also available in French
Edited and update: July 2013