The Red/Purple Line: An Alternate Method For Assessing Cervical Dilation Using Visual Cues

By Mindy Cockeram, LCCE

Today’s blog post is written by Mindy Cockeram, LCCE.  Mindy explores the “mystical” red/purple line that has been observed to provide information about cervical dilation without the need for a vaginal exam. – SM

When couples in my classes are learning techniques for coping in labor, such as the Sacral Rub (sacrum counterpressure), Double Hip Squeeze and Bladder32 accupressure points,  I always talk about the great position the partner is in for spotting the red, purple or dark line (depending on skin color) that creeps up between the laboring woman’s buttocks and how – by ‘reading’ that line – he or she may be able to assess more accurately the woman’s cervical progress than the health care providers!  This empowering thought is often met with smiles and laughter especially when I translate ‘natal cleft’ into more recognizable words like ‘butt cleavage’.  Strangely, I’ve never had anyone in class mention having heard of this ‘thermometer’ for accessing cervical dilation by sight and I find this interesting considering the number of medical professionals that come through my classes.

Photo CC http://www.flickr.com/photos/alexyra/214829536/

I first came across this body of research as an Antenatal Student Teacher with the National Childbirth Trust in London.  The article I was reading was in Practising Midwife and was a ‘look back’ at the original article (Hobbs, 1998) published in the same magazine.  The original Practising Midwife article was based on a letter referencing a small study by Byrne DL & Edmonds DK published in The Lancet in 1990.

In the 1990 letter to The Lancet, Byrne and Edmonds outlined and graphed 102 observations from eighteen midwifes on 48 laboring women. It states “The red line was seen on 91 (89%) occasions, and was completely absent in five (10.4%) women and initially absent in three (6.25%).”  The report then goes on to talk about the “significant correlation between the station of the fetal head and the red line length.”  Later the authors write: “To our knowledge, this is the first report of this red line.  We believe that it represents a clinical sign which is easy to recognize and which may offer valuable information in obstetric management.”

So how does this line work?  And why does this it appear?  Practising Midwife Magazine presented a graphic which I have attempted to recreate here.  Basically as the baby descends, a red/purplish (or perhaps brown depending on skin color) line creeps up from the anus to the top of the natal cleft in between the bottom cheeks.  When the line reaches the top of the natal cleft, 2nd stage is probably a matter of minutes away.  A line sitting an inch below the natal cleft is probably in transition.  A line just above the anus probably signifies early labor.

Byrne DL & Edmonds DK, the authors of the original study, surmise that the cause of the line is “vasocongestion at the base of the sacrum.” Furthermore, the authors reason that “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.”  Fascinating and logical!

Interestingly, I came across a 2nd Scottish study from 2010 published by BMC Pregnancy & Childbirth: (Shepherd A, Cheyne H, Kennedy S, McIntosh C, Styles M & Niven C) which aimed to assess the  percentage of women in which a line appeared (76%. ) The study cited only 48-56% accuracy of vaginal examinations to determine cervix diameter and fetal station.  So why aren’t clinicians using this less invasive visual measure – especially considering how much some women may dread vaginal exams in labor??  Wouldn’t the thought of using a methodology to lower infection rate after rupture of membranes has occurred enthuse Health Care Providers instead of using higher risk techniques?  Or how about using the accuracy of the line at the natal cleft to know when a women using epidural should really be coached to push?

My educated guess is that this information has not yet reached Medical Textbooks and non-standard practices can take years to become mainstream (for example. delayed cord clamping) – and then only if or when women request them or media sensation activates them.  In addition, since laboring women are only intermittently attended by Labor & Delivery staff during early and active labor and often encouraged to “stay in bed,” Health Care Providers aren’t necessarily faced with a woman’s buttocks in labor.  Also vaginal examinations are considered “accurate” so staff have no need to peek between a woman’s natal cleft.   However both these studies, paired with the roughly 50% accuracy rate of manual vaginal exams, show that there is potentially a more accurate and less invasive way ahead.

In The Practising Midwife (Jan 2007, Vol 10 no 1, pg 27), Lesley Hobbs writes “Accurate reading would seem to the key to this practice.  I sometimes notice in myself a wish to see the line progressing more quickly than it actually does; when I do this – and check with a vaginal exam – only to find the line is right, I get annoyed with myself and wish I’d trusted my observations.”  Later she goes on to say “I can now envisage a time when I shall feel confident enough to use this as my formal measurement mechanism and abandon intrusive and superfluous vaginal exams.”

Licensed Midwife Karen Baker from Yucaipa, CA commented “The purple line is a curious thing.  It’s definitely not present on everybody but is more prominent on some than others – especially right before pushing.  It tells us when she’s in full swing if we are in a good position to spot it!”

I often urge couples to send me a picture of the so called ‘purple line’ which I promise I will use only for educational purposes but so far a picture is as elusive as the Loch Ness Monster.  So, as I say in class, ‘show me your purple line’!

Are you a midwife, doctor, nurse or doula who has observed this in a client or patient? Partners, have you seen this when your partner was in labor? Has anyone heard of it or witnessed it?  If you are a childbirth educator, do you feel this is something that you might mention in your classes?  Do you think that the families in your classes might be likely to ask for this type of assessment if they knew about it? Please comment and share your experiences.


Byrne DL, Edmonds DK. 1990, Clinical method for evaluating progress in first stage labour.Lancet. 1990 Jan 13;335(8681):122.

Downe S, Gyte GML, Dahlen HG, Singata M. Routine vaginal examinations for assessing progress of labour to improve outcomes for women and babies at term (Protocol). Cochrane Database of Systematic Reviews 2012, Issue 9. Art. No.: CD010088. DOI: 10.1002/14651858.CD010088.

Hobbs 1998. Assessing cervical dilatation without Vaginal Exams. Watching the purple line. The Practising Midwife 1(11):34-5.

About Mindy Cockeram

Mindy Cockeram is a Lamaze Certified Childbirth Educator teaching for a large network of hospitals in Southern California.  She has a BA in Communications from Villanova University and qualified as an Antenatal Teacher through the United Kingdom’s National Childbirth Trust (NCT) in 2006.  A native of the Philadelphia area, she spent 20 years in London before relocating to Redlands, CA in 2010.





Childbirth Education, Guest Posts, Midwifery, Research, Uncategorized , , , , , ,

  1. avatar
    Georgia Mom
    July 20th, 2013 at 09:41 | #1

    I am 36 weeks pregnant with twins. My last cervical check, at 32 weeks, I was 2cm dilated, 25% effaced, and Baby A was very low. I just checked my “natal cleft” and there is a very clear reddish-purple line nearly all the way up it–high enough to suggest I might be 8 or 9 cm at the moment (which I rather doubt). I wonder if the increased pressure of twin pregnancies makes it more likely for the line to appear–and to appear higher–earlier? It’s all very interesting, in any case, and certainly more studies should be done on it.

  2. avatar
    Mindy Cockeram
    September 15th, 2013 at 19:31 | #2

    @Georgia Mom
    Interesting! I now wonder too (about twins) and agree more studies should be done. Best of luck and sorry for the delay in replying. Suspect you have your hands full by now.

  3. avatar
    October 25th, 2013 at 15:49 | #3

    At my last check up I was 3cm dilated,90% effaced and baby’s station is -1. I told my midwife that I had noticed the purple line which she asked to see. My line was almost exactly where it is in your picture. A reddish/pink line extends all the way up, but the purple line was just slightly up. I wonder if some people are mistaking the lighter line with the actual line which is much darker.

  4. avatar
    Melanie (doula)
    February 23rd, 2014 at 10:00 | #4

    Yes, I have seen the purple line in a client. It was all the way up the natal cleft when she was in second stage labor (pushing). Right on!

  5. avatar
    April 17th, 2014 at 17:59 | #5

    i wonder if the line shows even if the baby is high.
    In both pregnancies my babies were high and I’ve been wondering of that line has something to do with baby’s position.
    Maybe the woman that doesn’t show it have high babies so there isn’t pressure to produce the line?
    perhaps it has to do with dilation and descend?

  6. avatar
    July 10th, 2014 at 06:48 | #6

    I just re-read the birth notes from my doula from the birth of my second child which took place in the birthing center of a hospital. She states “.. I and the midwife were sure you were fully dilated or very close. You were now spontaneously pushing through the peak of every contraction and had an ever brightening purple line running up from the top of your bottom – a sign of full dilation”..
    Well I never saw this myself, my baby was OP and I was a bit stressed out by then and past frustration. But they were right and the baby was finally born shortly afterwards. We’re based in London. If my husband would have taken photos I would probably have … him.

  7. avatar
    August 12th, 2014 at 23:46 | #7

    Wow! This is interesting! I’m currently pregnant with my 3rd baby and have NEVER heard of this even though I’ve done extensive research on holistic pregnancy and birth and opted for a holistic birth center for my last child (and this one). Does Ina May Gaskin mention this in her research at all? I’ve read a lot of her work but don’t remember this. If I had a line, the midwife and nurses would definitely have been able to see it last time since I was on the bed leaned over a birthing ball most of the time. This would have been helpful knowledge before I went to the birthing center last time since I didn’t know how progressed I was (I went in at 8 cm) and told my husband to leave everything in the car just in case they said to go back home :)

  8. August 18th, 2014 at 21:36 | #8

    I often watch this purple line with clients in labour. A wonderful tool.

  9. avatar
    August 19th, 2014 at 07:48 | #9

    My fiancée is pregnant with our first kid. I’m very interested in this whole pregnancy. I’ve done the vaginal exam myself on her. We went into the hospital because we thought her water broke, she was 5cm they didn’t keep her because she isn’t experiencing labor pains, she had high pain tolerance. When we got home I was looking up other ways to check dilation and ran across some articles talking about this purple line. We tested it out that day sure enough it read 5 cm. So we’ve been doing it everyday and she almost measures 7 cm now but again she isn’t feeling the pain they want her too feel. So we sadly wait for the due date…which is only 2 weeks away!!! (September 3rd)

    Medical professionals should jump on this and see how accurate it is compared and make it more known. NO one we’ve mentioned it too has ever heard of it!

  10. avatar
    August 24th, 2014 at 14:53 | #10

    I have just learned about this purple line, and i am with my third child. Earlier this weekend I had a internal exam that said i was at 2cm, so I checked and found that yes I have this line, but I am very confused as to how to understand the length of the purple line to the the dilation of the cervix{example I am 2cm does that mean the line should be only 2cm?}

  11. avatar
    December 2nd, 2014 at 17:45 | #11

    I currently have a red line that would suggest 7-8 cm, but I have no dilation from what I have been told and are 38 weeks pregnant, just notice the line tonight..Interesting

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