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RaMa Mama Doula Share: "What is the Purple Line" Measuring Tool?...

Checking for the station of the baby's head and dilation during labor is a controversial topic. Some say that each time a mother has a vaginal exam, she is putting the baby at risk of infection. Many midwives don't believe in physical checks until right before it's time to push, especially when the bag of waters has been broken. This leaves most in the dark in knowing where the baby and mother are in the birthing process.

In about 75% of pregnancies, the "purple butt line", or Natal Cleft, appears to tell us where the baby is in the body. The station of the baby's head is much more important than how dilated the mother-to-be is at the time, because dilation will never explain timing. Some women dilate all the way to 8cm very quickly, and then take another 12-24 hours to get to 10cm. Knowing where the baby is in the canal and how the mother is coming along can be extremely supportive in the birthing process.

This Purple Line runs from the anus vertically to the top of the natal cleft in between the butt cheeks. It is said that this line starts to form when the cervix is between zero and two centimeters dilated. As the baby descends into the pelvis, the purple line rises up to the surface. This occurs because of vascular congestion in the lower sacrum area. The more the baby's head descends, the more pressure on the pelvis, and the greater the length of the purple line.

As this test is not a perfect measure of cervical dilation, it is a great tool that can be very helpful. For some mothers, the line is very faint, and for others it can be dark or even look like a bruise. It has been recorded that the purple line, which has been seen as brown and red on different skin types, can show up even before labor begins as a sign that the body is getting ready to give birth.

Use this chart as a helpful reference to help determine how far along the mother is. Keep an open mind when it comes to birth. No one has all of the answers and every birth is completely different from the last. The more information we have, the more helpful we can be when the time comes.

Purple Line Test Estimated Results

3-6cm Purple Line = 1-2cm dilated

5--8cm Purple Line = 3-6cm dilated

7-9cm Purple Line = 7-8cm dilated

8-11cm Purple Line = 9-10cm dilated


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