Updated: February 2022
One of my failings as a midwife is my inability to assess the strength and effectiveness of a uterine contraction. This presents a problem in the hospital setting as midwives are often asked ‘how strong are her contractions?’ or ‘is she having effective contractions?’ I spent many hours as a student midwife with my hands on women’s abdomens attempting to assess their contractions. Not only was I unsuccessful, but I was probably very irritating and disrupted physiology (apologies to those women). While it may be possible to find out how often contractions are coming, and how long they are lasting – I dispute the idea that you can assess how effective or strong they are this way. This post will discuss contractions and whether it is possible to determine their effectiveness and whether we need to.
A quick history lesson
The idea that birth should be efficient has its roots in the 17th century when men used science to re-define birth. The body was conceptualised as a machine and birth became a process with stages, measurements, timelines, mechanisms etc. This is still reflected in current textbooks, knowledge and practice.
The legacy of Friedman’s curve
In the 1950s Emanuel Friedman created a graph of labour based on his research of 500 women having their first baby. These women were subjected to rectal examinations every hour during their labour. You can apparently feel the cervix through the rectum! Most of the women in the study were sedated, and had medication (Pitocin) to speed up their labour. The final graph is the basis for modern assessments of labour progress. However, there are variations between hospital policies regarding adequate progress. For example, a cervix can open 0.5cm an hour in one hospital and be adequate, whereas in another it must open 1cm per hour to be adequate. Now I could do an entire post (and might do in the future) on the ridiculous notion that you can apply a graph to something as complex and unique as a birthing woman (edit – I wrote a book instead). However, I think the evidence speaks for itself. More than half of all women who experience labour in Australia have their labour either induced or augmented. Therefore, inadequate progress is the norm… or our definition of adequate progress is wrong.
How a contraction works (overview)
The hormone oxytocin (heart) regulates contractions, and it is released from the hypothalamus (primitive brain). The uterus has oxytocin receptors which respond to oxytocin by initiating a contraction. Contractions start in the top of the uterus (fundus) and ‘wave’ downwards. The cervix must be ready (ie. ripe) before it will respond to contractions by opening. This is why induction usually involves preparation of the cervix with prostaglandins before starting a syntocinon (pitocin) drip to create contractions. When the uterus contracts the placental circulation is reduced (more so if the waters have broken), slightly decreasing the oxygen supply to the baby. This is why there are breaks in between contractions – to allow the baby to rebalance their oxygen levels before the next contraction. If you’re wanting a reference for the above, any anatomy and physiology text book will cover this basic physiology. If you want a more in-depth understanding, see my Book or my Online Course.
Note: Oxytocin (syntocinon/pitocin) administered via a drip is not released in waves and an individual woman’s oxytocin receptor response is unpredictable. This may result in contractions that are too powerful without an adequate gap between them leading to a hypoxic baby – similar to what happens during directed pushing.
The psychological / emotional component:
Oxytocin is influenced by, and influences, feelings and behaviour. There is a growing body of research exploring this aspect of oxytocin. Basically oxytocin is part of the hormonal cocktail that prepares a mother and baby for bonding and attachment. The hormonal formula is: oxytocin (love) + beta-endorphin (dependency) + prolactin (mothering) = mother-baby-bond.
Note: Oxytocin does not cross the blood-brain barrier. Therefore, only oxytocin produced in the brain has these psychological/emotional effects. Syntocinon/pitocin administered via a drip into the blood stream only acts on the uterus ie. contractions.
Contractions are measured according to how often they occur in a 10 minute period and are recorded as 2:10, 3:10, 4:10 etc. To be considered ‘effective’ contractions need to occur 3:10 or more and last for 45 seconds or more. From a mechanistic perspective it would be impossible to progress through labour with 2 contractions or less every 10mins. I actually believed this for a some time – until women showed me otherwise.
What I now know is that a woman’s contraction pattern is unique. I have witnessed women birth babies perfectly well with very ‘ineffective’ contraction patterns. The recent ones that stand out in my mind are: A woman with an OP baby whose contractions never got closer than 5 minutes apart and were mostly 7-10 minutes apart. And a first time mother who birth her baby with mostly 10 minute spaces between contractions. When left to birth physiologically, women’s labour patterns are as unique as they are. Unfortunately, many midwives are unable to witness a variety of contraction patterns because individuality is not tolerated in the hospital setting.
I have already mentioned that I don’t believe you can do this by touch (cue a hundred comments from midwives who can!). Observing a woman may give you some idea, especially if you have seen a change in her behaviour (sound, movement etc.) over time and/or know her well. But again this is subjective and I’m sure many midwives have been caught out by women who appear to be doing ‘nothing’, but actually are, or appearing to be about to birth when they are not.
Using dilatation of the cervix to determine the effectiveness of contractions is also unhelpful – see this post about routine vaginal examinations.
Sensible assessment of contractions
Induced or augmented labour
Over-contraction and/or fetal distress are common complications associated with using syntocinon/pitocin in labour. It is essential that a CTG machine is used to closely monitor the baby’s heart rate. A midwife should also use her hands to assess how often contractions occur, and for how long, because CTG machines are not very good at this. Again, CTG machines, like midwives, can only tell you how often contractions are occurring and hint at how long they are lasting.
Every woman’s contraction pattern is unique and applying graphs routinely does not improve outcomes and leads to unnecessary intervention. A physically obstructed labour is rare and can be identified by frequent, long-lasting contractions over many hours with no change in the pattern of labour, or position of the baby. Women often ‘know’ there is something ‘wrong’. Eventually, the baby may begin to show signs of distress. However, most ‘obstructed labours’ are psychological/emotional (see above) rather than pathological, and if the environment is changed, the labour will progress. Indeed, observation of the woman and her contraction pattern may actually interfere with her oxytocin release and obstruct her labour.
Note re. VBAC: A change in contraction pattern from regular contractions to irregular or uncoordinated contractions may be a sign that the uterine scar is beginning to tear. This is very rare (0.5%) and more likely with IV syntocinon/pitocin.
You cannot assess the effectiveness or strength of a contraction. An effective labour pattern is one where mother and baby are well, and there is some kind of progress over time. Instead of assessing contractions, midwives should concentrate on creating an environment that supports oxytocin release. This may mean not being in the room or not observing the woman. Avoiding talking to a woman during a contraction is very important for all those attending her birth.
You can learn more about Childbirth Physiology in my Online Course