The purple line as a measure of labourprogress: a longitudinal study

Abstract

BackgroundVaginal examination (VE) and assessment of the cervix is currently considered to be the gold standard for assessment of labour progress. It is however inherently imprecise with studies indicating an overall accuracy for determining the diameter of the cervix at between 48-56%. Furthermore, VEs can be unpleasant, intrusive and embarrassing for women, and are associated with the risk of introducing infection. In light of increasing concern world wide about the use of routine interventions in labour it may be time to consider alternative, less intrusive means of assessing progress in labour. The presence of a purple line during labour, seen to rise from the anal margin and extend between the buttocks as labour progresses has been reported. The study described in this paper aimed to assess in what percentage of women in labour a purple line was present, clear and measurable and to determine if any relationship existed between the length of the purple line and cervical dilatation and/or station of the fetal head.MethodsThis longitudinal study observed 144 women either in spontaneous labour (n = 112) or for induction of labour (n = 32) from admission through to final VE. Women were examined in the lateral position and midwives recorded the presence or absence of the line throughout labour immediately before each VE. Where present, the length of the line was measured using a disposable tape measure. Within subjects correlation, chi-squared test for independence, and independent samples t-test were used to analyse the data.ResultsThe purple line was seen at some point in labour for 109 women (76%). There was a medium positive correlation between length of the purple line and cervical dilatation (r = +0.36, n = 66, P = 0.0001) and station of the fetal head (r = +0.42, n = 56, P < 0.0001).ConclusionsThe purple line does exist and there is a medium positive correlation between its length and both cervical dilatation and station of the fetal head. Where the line is present, it may provide a useful guide for clinicians of labour progress along side other measures. Further research is required to assess whether measurement of the line is acceptable to women in labour and also clinicians.

The frequency and reasons for vaginal examinations in labour

“…Hobbs article was cited as one of the key midwifery papers to be published in the last 10 years due to the debate that followed of alternative, less invasive ways, of assessing women's progress in labour. 30 The study by Shepherd et al 16 of the purple line was the first to consider measurement of this line as a means of monitoring labour progress. The results from this study showed that there was a correlation between the lines length with both cervical dilatation and station of the foetal head.…”

Labour augmentation and fetal outcomes in relation to birth positions: A secondary analysis of an RCT evaluating birth seat births

“…Apart from non-compliance, major problems in RCT research are high dropout rates and selection bias due to reliance on midwives in identifying appropriate participants. These problems result in 18 difficulties in assessing the generalisability of trials (Hundley & Cheyne, 2004;Shepherd et al, 2010).…”

Use of the purple line to diagnose cervical dilatation and fetal head station during labor

“…The purple line is a red–purple spot that appears around the anus during labor in parallel with progression of cervical dilatation . Its physiology is not well established and its appearance and growth during labor has been reported to be related to pelvic vascular congestion . The aim of the present study was to estimate the incidence of the purple line and if it can supplement the evaluation of labor progression.…”

“…1 Its physiology is not well established and its appearance and growth during labor has been reported to be related to pelvic vascular congestion. 2,3 The aim of the present study was to estimate the incidence of the purple line and if it can supplement the evaluation of labor progression. A prospective cohort study enrolled 220 women who were hospitalized for labor or induction of labor between 1.12, 95% CI 1.02-1.23; P=0.023) and premature rupture of membranes (aRR 1.15, 95% CI 1.01-1.32; P=0.042) were associated with increased risk of the purple line being identified ( Table 1).…”