Alternative Methods of Checking Dilation {The Purple Line and More}

by Mama Bice on June 6, 2013

Through several years of being a part of the birth world I have noticed a trend. Dilation is *the* birth topic. No matter how a mother plans to birth, when the time draws near, dilation is the one thing on her mind. Why? Cervical dilation tells us one thing and one thing only – where you are right that second. It tells you nothing about what came before that check (when you compare to other labors or women) and it tells you nothing about what is to come. It only tells you about the here and now.

cervical check

The news of little or a lot of dilation can either help or hurt a mother’s mental state in labor. If the mother has been in early labor for days (which is normal), the news of a only 1 or 2cm of “progress” can completely take her out of a peaceful state of mind. If the mother has only been in labor for a few hours and finds out she is already at say, 7cm, she may think her time is nigh…only to find out that she has many more hours of work ahead. Basically – the information can back fire on you.

But there are times when the information can be of use. For instance, a mother may plan to wait to get an epidural until “x” dilation. Or she may be waiting to call her family until she is sure things are really cooking. So what are the ways of getting this information? The first thought that comes to mind (and the only thought usually) is that you must have a vaginal exam.

Guess what? You don’t! That’s right – no one has to put their hands in your vagina to give you this information. Vaginal checks come with their own set of risks, from accidental rupture of membranes (or not so accidental – some care providers have used it as a good time to break mother’s water without asking) to increased risk of infection.

Studies also show that vaginal exams are not really accurate. When checking for exact dilation, studies show the accuracy to be around 48-56%. When allowing a margin of 1cm (which is a large margin of error when this information is used to time interventions or labor “cut-offs”) the accuracy is around 89-91%. [One such study abstract from real women in labor. And another study abstract which was done on models.] When you add in multiple people checking, the accuracy gets even worse. Yet, vaginal exams are considered the “gold standard” of assessing labor progress. And lets not forget that vaginal exams are just plain uncomfortable at the best of times – in labor they can be downright hellish.

So what are some ways of figuring out your dilation without actually touching the cervix?

The Purple Line or Bottom Line

This is a purple/dark line that shows up and extends well, to put it delicately, along your natal cleft. Or rather – your butt crack. The line starts at the anus and moves up the cleft. When it is all the way to the top, you are 10cm. Normally – you do have a bit of a line there. But this Purple Line or Bottom Line is not he line that is normally there (which is usually pink). This is a dark purple line. My suggestion is to check out your bum in early pregnancy so that you know the difference.

A study was done in 2010, and published by BMC Pregnancy & Childbirth, that proves the existence and accuracy of the purple line for many women. In this study, the line itself was present at some point in labor for 76% of women. The line was more apt to show in women with spontaneous labor than in those with induced labor (80% vs. 59%). The further dilated a woman was, the more likely she was to have the line show up. The line showed up most when women were around 7-8cm dilated, and seemed to fade in some women at almost complete dilation. And according to this study sample, the line seems to first show for most women around 3-4cm.

An earlier study was done in 1990 and published in the Lancet which also proved the existence and accuracy of the line, though the sample size was smaller. In this study, the line was seen about 89% of the time and was only completely absent in 10% of women. They noticed a significant correlation between the station of the baby’s head and the length of the line.

The reason for the Purple Line is believed to be due to the increased pressure on the veins around the sacrum. This pressure on the veins creates the dark line where the thin skin of the cleft can show it. This pressure from the head creating the line also means that you can reasonably assess the station of the baby’s head as it moves down. Lower head = more pressure = higher line.

Here is a great example of the Purple Line from a wonderful mother in our support group. Obviously – she is complete in this photo, and baby is on its way out! But you can see the Purple Line so clearly (though I did take the liberty of highlighting it for you). Thank you Sara for sharing this moment with us!

purple line

With the relative accuracy of this method, and especially considering the inaccuracy of vaginal checks, this is a great way for women to check themselves without “checking”. This would also be a pretty accurate way of judging when to head to the hospital (if that is your plan) if you are one of the 76% of women this line shows up for.

The photo below is from Jackie, who was so excited when her purple line showed up around 8cm she actually asked her photographer to snap a photo!

Purple LIne

Sounds of Birth

The sounds a woman makes in labor can tell a care provider (or partner) much about where the woman is in labor. Obviously, this will not work the same for all women. Some women are noisy all the way through – which is fine. Some women are quiet until the very end – also fine and normal. However, there does seem to be a pattern for most women in the way they vocalize in labor.

In early labor (0 to 4cm) a women can normally converse easily or with little effort during contractions. She does not feel the need to rest between them very much, and will most likely continue or pick the conversation right back up after each contraction. In active labor (4 – 6 or 7 cm) the woman usually has to do some breathing or vocalizing during contractions, and normally stops speaking during them. She may have to rest more between them.

In transition (7 – 9cm) the woman tends to really need labor noises – groaning, moaning, and sometimes repetitive mantras or noises. At full dilation the women may really retreat within and become quiet. She may not want to speak at all, even between contractions. Pushing of course has its own set of noises. And just a note on noises – low and open noises seem to help women dilate. Keeping the jaw slack and not clenching helps the pelvic area to open and not clench as well.

Smell

This is something that birth workers will talk about and recognize. Just before the start of transition, the woman emits an earthy and very “birthy” smell. Musky and deep, it speaks to some inner part of our being and psyche.

Fundal Height

This is a documented way of measuring dilation externally. When not in labor and full term the fundal height is normally 5 finger-breadths between the fundus (top of the uterus) to the bottom of the breast bone. As labor progresses, the uterus pulls up on the bottom of the uterus (which is the cervical opening) and this is what creates dilation. Think of it as the uterus “bunching up” at the top in order to pull the bottom up and open.

As dilation progresses, the finger-breadths between the fundus and the breast bone becomes smaller and smaller – at full dilation, you can normally no longer find the gap between the two. This measurement must be done at the height of the contraction, and while mother is on her back. This means it will not be the most comfortable way of assessing progress – but it does work.

Emotions

Basically – as a mother gets more serious, her dilation is increasing. Naturally (like with noise/vocalizations) this is not true for all women. However, in reading birth story after birth story (and watching video after video) I do see this trend. Mothers start out chatty and light hearted. As the harder work sets in, mothers retreat inside and tend to ignore those around them or get serious in other ways.

This seems to be a very accurate sign of transition for most women. Transition is typically the last stage of dilation and is normally the most intense. It is during this stage that mom may get irrational or scared. Usually this is when women feel the “I can’t do this” emotions and may express sudden fear or want of pain medication. When women are prepared for this stage they can be reassured that this means labor is almost over and baby is near.

Bloody Show

Many women hear about the bloody show at the start of labor. Not all women have this, but it is the “mucus plug”…basically, it looks like a large wad (or wads) of well – snot. I know, not the nicest way of saying it, but it is true. The mucus plug is probably one of the weirdest looking parts of labor and birth. However, around 6cm or so, most women get a another (or first) bloody show. This usually comes out during contractions, and may be a gush of fluids and mucus and blood. If a woman’s membranes were broken before this point, she may have another gush of fluid at this point.

Estimate Without Fear

All of these methods can be used to assess progress in laboring women. Some may be more accurate than others, but perhaps we should ask ourselves about why we want to know dilation in general. In some situations the information can be very useful, for instance if a mother does not want to head to the hospital too early or if she is negotiating for more time in labor but does not want a vaginal exam at the moment (or at all).

However, my suggestion is that for the average laboring woman we learn to not equate cervical dilation with progress or lack of progress. As I stated at the start, dilation is only a snapshot of where you are right now and tells you nothing about where you will be an hour from now or even 30 minutes from now. Long labors with slow dilation can suddenly speed up and reach full dilation (and baby in arms) in mere minutes or hours compared to the slow dilation of the previous hours or days. Women who are not dilated or effaced at all during a prenatal appointment can suddenly have a baby in arms an hour later. [Though, prenatal dilation checks are another subject that will need a separate post.] Dilation is simply not a crystal ball.

If you are a mother who wants to avoid cervical checks completely, or wants to know how to assess dilation before your care provider comes (or you go to them), then these methods can serve you well. As always, continue your own research and talk to other supportive women.

Further Reading

Bellies and Babies Blog on Dilation

Science and Sensibility post on the Purple Line

A Midwife’s Perspective on Cervical Exams

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