There's This Thing Called the "Purple Line"
Before you have a baby, you never knew how much you never knew. I'm about to drop some more knowledge on you today.
When you're in labor, you may or may not develop a purple line in your butt crack that can tell how dilated you are.
I'm not even lying. This study of 144 women in labor found that 109 of the women had this purple butt line, and to some degree it did correlate to the percentage of cervical dilation. I've even personally observed it when attending births as a doula!
The “purple line” is said to start appearing when your cervix is between zero and two centimeters dilated. This line can be very faint, or as bold as if you drew it on with a felt-tip marker, and it grows vertically. Some say that when it reaches the top of your crack, that means you're fully dilated.
The purple line during birth may be caused by the intense pressure on your veins in that area, and is probably easiest to spot on light-skinned moms. It would definitely make sense that the more your baby's head moves down and increases the pressure, the darker the color and the higher the line would grow!
For many moms, vaginal exams are uncomfortable or painful or triggering. However, a lot of times we are very curious to find out how dilated we are, so we ask to have an exam anyway. What if we could look for this line instead, as a means of determining dilation? This could be a great tool for your spouse or partner to look for as well while in early labor at home, trying to figure out if it's about time to go to the hospital or not.
Not every woman will experience "the purple line" as evidenced in the above study, and of course there are plenty of other legit reasons we shouldn't assume that we can always replace a vaginal exam if needed or wanted. But of course, it doesn't hurt to take a quick peek just in case, right? Right.