This article considers the importance of observing the physiological and behavioural cues exhibited by women during advanced labour to facilitate labour assessment. In-depth knowledge of labour physiology is important as it enables midwives to systematically anticipate, gather and interpret these cues while considering possible differential diagnoses. As a clinical midwife and educationalist, I have observed and participated in various care practices over the years within different birth environments. I have reflected upon how we can be instrumental in both supporting and impeding the physiological process of labour through the consequences of our actions.
The detrimental impact that routine intrapartum interventions can have upon the hormonal processes that support labour has been well-documented. Sara Buckley (2015) has written extensively about the importance of protecting the hormonal blueprint of labour through the avoidance of unnecessary intervention (see https://www.nationalpartnership.org/our-work/resources/health-care/maternity/hormonal-physiology-of-childbearing.pdf for an in-depth review).
As midwives, we are presented with a dichotomy within practice where we must endeavour to facilitate the physiological processes that support normal birth while staying alert for the presence of risk factors and instigating timely responses to ensure safe care. It is important we intervene only when clinically indicated. However, making this judgement can be difficult, especially when working in an environment where routine intervention is common. Intervening too soon can disrupt the physiological process of labour predisposing mother and infant to unnecessary risk and morbidities while intervening too late may also have detrimental consequences.
Over-reliance on invasive interventions may reflect a lack of confidence in our own skills of clinical observation, interpretation and assessment of the external physiological cues of labour (Bedwell et al, 2015; Skogheim and Hanssen, 2015).
It is imperative that we are familiar with the signs of normal labour processes so that we accommodate the variance that exists within the normal parameters of labour. This is because labour progress is not a uniform concept that can be applied consistently across populations or linearly within the same labour as it may vary across individuals, with periods of both acceleration and dormancy (Karaçam, 2014). Good physiological knowledge is essential to inform our skills of observation and interpretation which can be honed through our experiences of being with women in labour and watching the process of labour change.
Midwifery textbooks set out clearly the distinct physiological changes that may occur as labour progresses, and an overview of the physiological and behavioural signs observed by experienced midwives when assessing labour progress is presented in Table 1 (Nash, no date).
| Maternal changes observed by midwives during advanced labour |
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As labour advances, changes in the woman's demeanour become apparent as she focuses inwards to cope with the intensity of her uterine contractions. Vocal changes may be noticed and the woman may appear flushed and to enter a trance-like state. Close midwifery contact and supportive care are crucial at this point to engender a sense of safety and support maternal confidence and control in preparation for birth. Undertaking unnecessary vaginal examinations may disturb this process, causing avoidable stress for the woman, and the systematic assessment of external physiological cues along with the assessment of maternal and fetal well-being may provide assurance that labour is progressing normally.
Observation of the purple line as an indicator of labour progress has been documented widely within the midwifery literature. The purple line is observed as a dark reddish or purple line which can be seen when women adopt an all-fours position and commences from the maternal anal margin, and extends towards the maternal buttock cleft, reaching the nape of the buttocks at the onset of the second stage.
It is believed to result from the increased pressure on the veins around the sacrum and while there is limited research regarding the accuracy of the purple line as an external cue to assess progress in labour, preliminary findings are positive (Shepherd et al, 2010; Narchi et al, 2011).
Shepherd et al (2010) undertook a longitudinal study (n=144) to assess the effectiveness of the purple line as a measure of labour progress and found a positive correlation between the length of the purple line and cervical dilatation (p 0.0001) and station of the fetal head (p<0.0001). Masoumeh et al (2014) found high sensitivity and specificity with its use as a predictive tool to assess labour progress with an 87.6% sensitivity, 52.4% specificity and 96.5% positive predictive value (and 22% negative predictive value) for the second stage.
For those women who adopt an all-fours position, observation of the purple line may be a viable non-intrusive alternative option for assessing progress during advanced labour. In addition, the all-fours position, if adopted by the mother, may provide the midwife with opportunity to view the rhombus of michaelis named after the German obstetrician Gustav Adolf Michaelis who gained worldwide recognition for his studies on the ‘sacral rhombus’ (Grigorieva, 2020). This is viewed as a diamond- or kite-shaped curve on the mother's lower back, and is caused by displacement of the maternal sacrum and coccyx in advanced labour due to occipital descent (Howie and Watson, 2017).
The term ‘transition’ refers to the distinctive physiological changes that occur at some point during the end of the first stage and beginning of the second stage where women report feeling agitated, overwhelmed, panicky, fearful or drowsy (Roberts and Hanson, 2007). Midwives may notice a reduction in the frequency of maternal uterine contractions at this point providing a brief lull before the intensity of contractions recommences (Downe and Marshall, 2014).
During the active second stage, women without regional anaesthesia experience a strong urge to bear down or ‘push’. The advancing fetus gradually stretches the maternal cervix and vagina stimulating oxytocin secretion, facilitated by neural pathways called the Ferguson reflex (Feher, 2017) which strengthens uterine contractions. This combination of involuntary uterine contractions and voluntary muscles of the maternal diaphragm and abdominal wall assist the birth of the fetus (Coad and Dunstall, 2011; Downe, 2009).
Midwives may also observe how the woman's perineum appears to flatten and thin out as her pelvic floor becomes displaced as the mechanism of birth occurs (Downe and Marshall, 2014). Posteriorly, the maternal rectum is also flattened, meaning that the woman may open her bowels and anal gaping may be observed. The mechanism of birth refers to the series of movements that the fetus makes to negotiate the birth canal and knowledge of this is important as it enables the midwife to anticipate the next stage during the birth process as the fetus moves to optimise the space available within each plane of the pelvis.
Spending time in close proximity and being present with women in labour is crucial to enhance our observational and interpretational skills in relation to labour progress. Having the opportunity to work in intrapartum environments outside of obstetric units may be facilitative of this process of skill acquisition because, away from the perceived surveillance of the obstetric unit, midwives have opportunities to become closely acquainted with women's physiological and behavioural responses to labour (Davis and Homer, 2016; Reed et al 2016).
Such skills give us the confidence to accept the variation that exists within physiological labour and practice flexibly, incorporating an awareness of alternative explanations to inform our judgement. Flexibility has been identified as a component of expert midwifery practice (Downe et al, 2006; Downe and Simpson, 2011) and studies have described midwives' ability to work flexibly with uncertainty as an important construct in supporting normal labour (Page and Mander, 2014; Chodzaza et al, 2018). Good observational and interpretational skills can provide us with the confidence to employ watchful waiting and supportive care practices that empower women to feel in control and maintain a sense of ownership of their birth.