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Healthy Birth Practice #1: Let Labour Begin On Its Own

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March 16, 2023
Adapted from Giving Birth with Confidence, 3rd Edition.
Letting your body go into labor spontaneously is almost always the best way to know that your baby is ready to be born and that your body is ready for labor. In the vast majority of pregnancies, labor will start only when all the players -- your baby, your uterus, your hormones, and your placenta -- are ready. Naturally, labor usually goes better and parent and baby usually end up healthier when all systems are "go" for birth. Every day of the last weeks of pregnancy is vital to your baby's and body's preparation for birth.

If your labor is induced (started artificially), it becomes a medical event and proceeds quite differently from spontaneous labor. Unless you or your baby has a health problem that necessitates induction, it makes sense to wait patiently for your labor to start on its own. Even if your due date has passed and you're longing to hold your baby, remember that your body and your baby usually have good reasons for the wait.

For additional resources on induction, check out the following links:

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Lamaze Healthy Birth Practice: Let Labor Begin on Its Own

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Adapted from Giving Birth with Confidence, 3rd Edition. Letting your body go into labor spontaneously is almost always the best way to know that your baby is ready to be born and that your body is ready for labor.

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Assessing Progress Without Vaginal Exams

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At least once a month I get a request for a copy of a short piece about the purple line that I wrote a few years ago. It was during a journal's tenth birthday celebrations and a few of us had been asked to pick our favourite article from the first decade of the journal's history. The article would then be reprinted in the journal along with our explanation of why we had chosen it.

Because I picked Lesley Hobbs' fab article about the purple line, the short commentary that I wrote to introduce it (which has exactly the same title as this blog post, in the hope of saving future interested people time when they are searching for it online) often comes up in literature searches. In reality, the piece that I wrote (which I've shared below) was short and doesn't add much to the debate, although I have since written more on this topic and I have a blog post in which I have gathered together links to the resources that I know about.

But I know from my own experience that the only thing more annoying than not being able to find the short piece you're trying to track down is to spend time and money tracking it down, only to discover that it isn't the lengthy, helpful article that you thought it was!

So here's the text for those people who are searching for it and, because I think it's really useful to revisit and remind ourselves of key areas now and again, I hope this blog post will also serve as a reminder of the value of seeking other kinds of knowledge and looking for non-technological ways of assessing women's progress in labour.

Assessing cervical dilatation without VEs: Watching the purple line

What an exciting task ~ choosing an article to be reprinted! Having spent the last few years re-reading articles in order to gather the juiciest ones to be part of the "Midwifery: Best Practice" series, I already had a personal list of favourites and the article that I have chosen to be reprinted here is, as far as I am concerned, a real gem.

Lesley Hobbs' discussion of "the purple line" was originally published in the 'Midwife to Midwife' section of the journal, epitomises what was, for me, one of the key strengths of TPM when it was edited by Tricia Anderson and Jilly Rosser. Although Lesley's observations and reflections derive partly from the results of a study that was published in the Lancet, the bulk of the article consists of her own thoughts, reflections, experiences and questions in this area. It contains the kind of information that midwives often long for, but which isn't always forthcoming where the emphasis is on highly referenced, academically argued and scientifically based articles.

I believe that this article, along with a few others that were published around the same time, played an important part in enabling more midwives to think about alternative (to vaginal examination) ways of assessing women's progress in labour. The article generated debate (with some midwives noticing, for instance that the line is sometimes red and faint rather than obviously purple) and has been cited by a number of other midwives who have written about less invasive ways of assessing women's progress in labour.

Even though many midwives still work under systemic constraints in this area, and may be unable to rely predominantly on alternative ways of assessing women's progress, the fact that this kind of discussion and information exists is, to my mind, a very important aspect of cultural change. We may well still have a lot of work to do before assessment of the purple line and other aspects of women's behaviour become generally accepted ways of assessing labour progress, but, if the information and discussion is not there, we have no place from which to even begin the process of change.

Another reason for this article being one of my personal favourites is because of the way it generates excitement. I remember being excited when I first read the article; I had noticed a line on some women's bottoms during labour, and I had heard another midwife mention the original Lancet article, but I hadn't done anything specific to follow it up or find out more before Lesley's article was published.This article acted as a trigger for me to start my own observations, and, as above, it has been a trigger for ongoing discussion and debate amongst midwives; in person, at conferences and on the Internet.

This article continues to act as a trigger for students and midwives today. So much emphasis is placed on citing current evidence that, frankly, today's student midwives may not often open journals from 1998 unless they are looking for something specific. Almost every time I have suggested to a student midwife that they might like to find and read this article, they come back excited; excited about what Lesley has to say, and excited about the fact that they too might be able to learn just as much (if not more) from observing women as they can from their textbooks. For me, that alone entitles Lesley's article to a place in this celebration.

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Assessing cervical dilatation without VEs: Watching the purple line - Dr Sara Wickham

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At least once a month I get a request for a copy of a short piece about the purple line that I wrote a few years ago. It was during a journal's tenth birthday celebrations and a few of us had been asked to pick our favourite article from the first decade of the journal's history.

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I have been aware of the purple line being watched for, used and discussed by midwives for my whole career. I suspect that it has been known about and discussed for much longer than that.

In more recent times, people (including myself) began to write about and research it. And it's those studies and papers that I'm going to discuss in this blog post.

But there are a few important things you should know about the purple line before I get into the evidence.

First, it is seen a bit more easily in women with lighter skin. More on this below.

The so-called purple line is sometimes more red than purple. It can also be blue, brown, black, whitish, or pink, and I'm sure there will be more colours to come. So don't let its name fool you.

Why do I still call it purple, given that it can appear as many colours? Well, mostly because I work with academic and research tests, and that's how it is currently described in those. It's what people are searching for, and using any of those colours in the search box instead would bring up a LOT of articles which don't relate to this phenomenon at all! Equally, if I used other terms, my work wouldn't come up when others searched on the term that has historically need used. This is just one reason why it's really important to think about the wider context of knowledge, language and terminology.

And it is easiest to observe if a woman is leaning forward or on all fours. The purple line can also be seen if the woman is lying on her side. So it is not quite such a useful tool when women choose positions other than this. Many women far prefer having a midwife look for the purple line than doing a vaginal examination. Understandably, though, some don't want to have practitioners peering at their bottom either. And there are wider questions about to what extent we really need to assess progress in labour, but that's another story.

Let's start with the studies.

Byrne & Edwards (1990)

The purple line was first discussed in the literature (to my knowledge, but please see below) in a letter written to The Lancet by Byrne and Edmonds (1990).

They described the purple line as, a 'clinical sign which will indicate the progress of the first stage of labour without vaginal examination' (122).

Interestingly, they attributed a Sister H Lake as having first observed the purple line.

I think we can safely assume that Sister Lake was a midwife. Sadly, I can't confirm that. I have previously made quite a lot of effort to track her down, but without success.

Byrne and Edmonds' (1990) letter described how they had investigated the purple line in 48 women.

They saw the red line on 89% of occasions, but noted the existence of some women in whom the purple line wasn't seen at all.

Later research would confirm this and offer some interesting findings, but we'll come back to that...

Physiological origins

Byrne and Edmonds (1990) shared their ideas about the possible physiological origins of this sign:
'The line may arise because of vasocongestion at the base of the sacrum. It blanches when firm pressure is applied and slowly recolours when pressure is withdrawn. This congestion possibly occurs because of increasing intrapelvic pressure as the fetal head descends, which would account for the correlation between station of the fetal head and red line length ...
We postulate that increase in intrapelvic pressure causes congestion in the basivertebral and intervertebral veins around the sacrum, which, in conjunction with the lack of subcutaneous tissue over the sacrum, results in this line of red purple discoloration." (122).

Hobbs (1998)

I'm not sure how many midwives were aware of Byrne and Edmonds' (1990) article when it was first published, but many became aware after Lesley Hobbs, a British independent midwife, wrote about this in 1998.

Lesley explained Byrne and Edmonds' theory and discussed her own observations of the purple line in women, noting among other things that 'there is a longer gap between 4 and 7cm dilatation than there is both before and after' (Hobbs 1998: 34).

Although little happened on this in the literature for the next few years, this didn't mean the purple line was forgotten.

I saw evidence both in my day-to-day conversations and in the data I collected for various research studies that midwives (and a couple of obstetricians) were talking about the purple line and using this knowledge in practice, and I spoke about it at several conferences.

The experience of midwifery colleagues I met in countries such as Trinidad and Jamaica confirmed that this sign is sometimes less or differently visible in women with darker skin.

Shepherd et al (2010)

Narchi et al (2011)

The following year, Brazilian researchers published the results of a descriptive, prospective, observational study in 100 women in labor at a normal delivery clinic in the State of São Paulo.

They saw evidence of the purple line in 56 of the 100 women who were observed during the active phase of labour.

It should be noted that more than half of the participants in this study described themselves as Black or Brown. That's relevant because, as above, midwives at the time were reporting seeing it less in women with darker skin. The line was present in 27 of the 40 white women (67.5%) and 29 of the 60 non-white women (48.3%) in the Brazilian study. The authors note that, "the difference between the racial subgroups was not statistically significant," but this may well be because the study was small.

The researchers also report a statistically significant correlation between the measurements for dilation of the cervix and those for the line.

In 22% of the women, the purple line also became discoloured during labour. (I take 'discoloured' to mean changed colour, and this is something that has been noted by others. However I do not speak/read Portuguese and am relying on a translation of the article.) However, there was no association between the this discoloration and the extent to which the head of the fetus had descended in the cervix.

For 81% of the women, evaluation of the purple line in labour caused no discomfort whatsoever. When interviewed after childbirth, the other 19% said they felt ashamed, embarrassed or bothered. This was principally because they were asked to adopt the all fours position for the examination.

By contrast, however, 91% of the women expressed negative feelings about vaginal examination. They reported pain (7%), discomfort (40%), feelings of embarrassment (4%), disrespect (4%), fragility (1%) and fear (1%). Only 9% of the women stated that a vaginal examination had not caused them any discomfort.

Narchi et al (2011) concluded that measurement of the purple line could be used to reduce the number of vaginal examinations, especially when the only aim of the examination is to measure dilation of the cervix.

Kordi et al 2014

The next study that I'm aware of was carried out in Iran.
"In this cross-sectional study, 350 women with a single pregnancy in vertex presentation and gestational age of 38-42 weeks without any medical disorder, admitted to government hospitals of Mashhad, were selected using convenience sampling. Vaginal examination and observation of the line each hour in the active phase of labor were measured." "The purple line appeared in 75.3% of women during the active phase of labor. Appearance of the purple line in the prediction of labor progress had 90.2% sensitivity, 45.3% specificity, 88.1% positive predictive value, 51.0% negative predictive value in the first stage of labor and had 87.6% sensitivity, 52.4% specificity, 96.5% positive predictive value, 22.0% negative predictive value in the second stage of labor and has 68.57% sensitivity, 42.66% specificity, 85.32% positive predictive value, and 43.85% negative predictive value for the total labor."
"According to the appearance of the purple line in most of the cases and its high sensitivity and specificity, we can use it as a non-invasive complementary method for clinical assessment of labor progress." (Kordi et al 2014).

Wider conversations

I want to pause to note that the purple line was being discussed in other ways as well at this time.

I and a number of midwifery colleagues were discussing this at conferences, and raising questions about non invasive methods of assessing the progress of labour.

We were also raising questions about whether the progress of labour needed to be assessed in the way that the technocratic model argued that it did.

A number of papers questioning the practice of vaginal examination were also being published.

Nunes et al 2018

Nunes et al (2018) published their findings in a letter to the International Journal of Gynecology and Obstetrics.

In their study, the purple line was seen in 189 of the 220 women, which is 85.9%.

They noted the presence of the line in both spontaneous and induced labours, and also speculated that it might also be associated with premature rupture of membranes.

Nunes et al (2018) also found that white ethnicity was associated with a 12% higher chance of identifying a purple line.

They concluded that the purple line, "...had high incidence but was not suitable for diagnosing cervical dilatation and fetal head station owing to low accuracy." (Nunes et al 2018).

Farrag et al (2021)

The next published study was carried out in Egypt and included 120 labouring women.

Farrag et al (2021) found that, "the purple line appears among about four fifth of the total sample. A medium positive association was found among the purple line length, dilatations of the cervix and fetal stations. The purple line appearance in the expectation of labour progress had 87.91% sensitivity, 39.53% specificity and 85.25% accuracy."

Like Shepherd et al (2010), Farrag et al (2021) found that the purple line was more likely to be seen in women experiencing spontaneous labour than in those whose labours had been induced.

However, they found no significant association with parity, age, BMI or the baby's birth weight. We must again remember that these studies are small. It's also not clear in many of them how the samples were selected and whether this could have influenced the findings.

Farrag et al (2021) concluded that, "The purple line is useful in assisting the health care providers in assessing and determining labour progress and lessen the number of vaginal examinations, particularly at onsideration of females who refuse or feel that the examining intrusive."

Papoutsis et al's (2023) systematic review

More recently, a systematic review by Papoutsis et al (2023) brought together these studies on the purple line. The authors included all of the studies that I have shared on this page.

Here are their findings:
"There were six eligible studies included in the systematic review that reported on 982 women in total with the purple line appearing in 760 (77.3%) of cases. We found a moderate positive pooled correlation between the purple line length with cervical dilatation (r = +0.64; 95%CI: 0.41-0.87) and fetal head descent (r = +0.50; 95%CI: 0.32-0.68).
For women either in spontaneous or induced labour, the pooled mean length of the purple line was more than 9.4 cm when the cervical dilatation was 9-10 cm, whereas it was more than 7.3 cm when the cervical dilatation was 3-4 cm." (Papoutsis et al 2023)

Issues with methods

As I have noted throughout this post, all of these studies are small. For this and other reasons, we can't be as certain about their findings as we could if they had been designed differently. Papoutsis et al (2023) have discussed the issues with the research methods at length. Both Shepherd et al's (2010) study and and Papoutsis et al 's (2023) discussion should be useful to anyone looking to do more research.

It's important to note, however, that it is notoriously difficult to carry out large studies on topics like this one. Large studies require significant funding. Funding tends to come from pharmaceutical and technology companies, and from government-affiliated bodies.

I write from experience.

In conclusion...

So there is definitely room for more research, but we have learned a few things from these small studies.

The purple line can be a useful means of estimating the progress of labour in women whose bodies show this sign.

It's not infallible, exact, or perfect, but then neither is vaginal examination. As vaginal examination is painful, uncomfortable and embarrassing for many women, we would do well to keep exploring other means of estimating labour progress.

It would be fascinating to know why the purple line seems to appear more often when women go into labour themselves.

The purple line can be seen in darker skin more often than we once thought, but not as often as it can be seen on white skin. We clearly need to spend more time learning how to assess how this and other clinical signs may present differently in people with different skin tones.

I'm excited to see what we learn about this and other less invasive means of assessing labour progress in years to come.

What else can we learn?

Finally, I said above that Byrne and Edmond's (1990) letter was to my knowledge the first time that this sign was discussed in the literature.

Having seen the purple line many times myself, though, I find it hard to believe that Sister Lake was the first birth attendant to notice it.

I often wonder whether, one day, someone doing some historical midwifery research will come across an even earlier reference to this in old texts.

Or perhaps in other eras it was so well known and accepted that there would have been no need to even mention it.

One last note, which I have added after seeing some social media posts on this topic. If you see someone claim that they can tell exactly how far along a woman is by the purple line, that they can always see it, or that it's a better means of assessing progress than vaginal examination, that's a time to worry about their honesty or integrity. Phenomena like the purple line offer us a rough guide, and do not constitute an exact science. But the same is true of every other assessment of progress, including when we measure cervical dilation by vaginal examination. Humility in the face of knowledge is a wonderful thing.

References

Byrne DL & Edmonds DK (1990). Clinical method for evaluating progress in first stage of labour. Lancet 335(8681): 122.

Farrag R, Abd N, Eltohamy E (2021). Accuracy of purple line to monitor labour progress: Longitudinal study. Egypt J Health Care, 12 (1): 30-44.

Hobbs L (1998). Assessing cervical dilatation without VEs: watching the purple line. TPM 9(11): 34-35.

Kordi M, Irani M, Tara F et al (2014). The diagnostic accuracy of purple line in prediction of labor progress in Omolbanin Hospital. Iran. Iran Red Crescent Med J 16: e16183.

Narchi N, Camargo J, Salim N et al (2011). The use of the "purple line" as an auxiliary clinical method for evaluating the active phase of delivery. Rev Bras Saude Matern Infant 11: 313-322.

Nunes RD, Locatelli P, Traebert J (2018). Use of the purple line to diagnose cervical dilatation and fetal head station during labor. Int J Gynaecol Obstet 141(2): 250-251.

Papoutsis D, Antonakou A, Gornall A et al (2023). The purple line and its association with cervical dilatation in labour: A systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol 289: 91-99.

Shepherd A, Cheyne H, Kennedy S et al (2010). The purple line as a measure of labour progress: A longitudinal study. BMC Pregnancy and Childbirth 10 (54).

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