"Can you see that bulge on her lower back?" midwives from Tangi Birth Services write on Facebook. "That is the rhombus of Michaelis."
The image was initially shared by North Dallas Doulas on Instagram, earlier this year, who noted that the rhombus of Michaelis is the "kite-shaped area that includes the three lower lumber vertebrae, the sacrum and that long ligament which reaches down from the base of the skull to the sacrum."
The midwives explain that during the second stage of labour, a combination of bones, including the sacrum, move backwards. "In doing so, it increases the diameter of your pelvis," they write, adding that this is what is known as "opening of the back."
"This is completely normal," the midwives continue, "and is in fact an integral part of a physiological birth as it allows your baby the maximum amount of space to turn as they navigate their way out into the world."
To facilitate this, the midwives note that you should use "active birth positions" where you're upright and leaning forwards.
"While your pelvis is expanding, your baby's head is moulding - changing shape to fit through those pelvic bones!" they continues. "Your body was made to do this! And your body and your baby work together!"
Melissa Espey-Mueller, who took the original photo and is the owner and director of North Dallas Doula Associates, said it's something she'd been trying to capture for years,
"I have been a doula for 20 years and have been eager to find a photo showing this physiologic occurrence for some time," she told
Mom.com. "When I had the opportunity to snap this picture and share it with the mother's permission, I was thrilled."
The image has since gone viral, shared over 50,000 times as of Monday morning, and attracting thousands of comments.
"My husband told me about this!" writes Vanessa Barnes. "I give birth on my knees and he said the base of my back pushed out. Fascinating to see a photo of it."
"The more I read about childbirth and labour the more new things I learn about our bodies as women," says Shanice Darling. "It's truly an amazing experience. Powerful, exhilarating and I truly feel like the goddess I am to bring life into this world."
One woman even recalled feeling the sensation itself.
"When my bones shifted for birth I felt a pop like when you crack your knuckles and it felt SOOOOO GOOD!!!" writes Laura King. "I had been having terrible back labor pain and then POP and just this extremely wonderful release and the pain was gone. So amazing."
For Espey-Mueller the photo reiterates the importance of women listening to their bodies and labouring in a position that's right for them.
"This mum is actually on her knees facing and leaning over the head of the bed to allow her the ability to not bear all her weight on her legs," she said. "If she was lying on her back, this entire area would have been closed off and it would have prevented her baby from descending as easily, and made the transition and pushing phase longer.
"Since she was able to listen to her body and communicate her feelings to me, I was able to suggest this position which allowed for a very fast delivery."