There is a “mystical” red/purple line that has been observed to provide information about cervical dilation without the need for a vaginal exam.
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.”
To find out why, and more about assessing your labour through the red/purple line see the full article.
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%. ) This study cited only 48-56% accuracy of vaginal examinations.