Photo by Ryan Franco

Editor’s note: This article first appeared in Midwifery Today, Issue 127, Autumn 2018.
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Birth. One word, one syllable, five letters, and the transformative power of the universe. I am accustomed to being conscious of, in tune with, and in awe of the outward power of birth. The messy, beautiful making of a family. The gritty, earthy humanness of the work.

Birth workers are acutely aware of the strength it takes to walk through that veil and emerge on the other side with the promise of new life. We see it with our eyes, hear it with our ears, and feel it with our hands and hearts. All of our senses are engaged in and dedicated to supporting the process. We understand the holistic nature of birth and labor—that we must support the entirety of the woman to facilitate birth. But what about the unseen? The part of ourselves that is able to harness life itself. The furnace that holds the flame and secures and nurtures the future of humanity.

The non-pregnant uterus weighs approximately 50 gm, is often compared to an upside-down pear, and is situated deep in the pelvis. It is made up of three layers. The outer, or peritoneal, layer is continuous with the serosa of the peritoneum and sheathes the uterus in a thin membrane, helping to keep it in place. The middle layer, or myometrium, is composed of smooth muscle. The inner portion—the endometrium—is made up of ciliated cells. These layers are further divided among themselves, layer upon layer, laying the foundation for the growth and development of the pregnancy. Each is necessary and interconnected as part of the whole.

The endometrial layer is made up of two parts: the stratum functionalis and the stratum basilis. Each month the stratum functionalis thickens and, when there is no pregnancy, is shed as part of the menstrual cycle. Behind that is the stratum basalis, the layer that remains and creates the new stratum functionalis with each cycle. In the endometrium, the developing blastocyst, then embryo, then baby is nurtured. It is the site of implantation and where the placenta will grow. The nest of warmth, blood, and oxygen that fans the flames of life and soul.

The myometrium is the workhorse of the uterus, the smooth muscle that stretches to accommodate the growing baby and placenta. It is where the contractions that help to expel the baby during the birth process originate. These muscles are further divided into three more fibrous layers:

The inner fibers run in a longitudinal pattern, from the anterior cervix up over the fundus and back to the posterior cervix.

The middle layers create a spiral of interlaced fibers that begin over the fundus and spread down, dense to less dense, as they flow down to the cervix.

The outer fibers are comprised of both longitudinal and circular fibers that encircle the myometrium.

These three layers hold within themselves the immense power required to birth our babies, yet they are fluid and pliable enough to allow for immense change.

Uterine changes begin almost immediately with the fertilization of the ovum. By six weeks, there are four objective signs that pregnancy has taken root. As the vulva, vaginal mucosa, and vaginal portion of the cervix become enriched with extra blood flow, they take on a blue-purple coloring known as Chadwick’s sign. Goodell’s sign is noticeable with the softening of the cervix and a palpable softening of the isthmus—or Hegar’s sign, which can be detected by well-trained hands. In a typical pregnancy, the first area of the uterus to change in shape is the coronal zone—the areas where the fallopian tubes meet the uterine fundus. This causes an asymmetry known as Piskacek’s signs and is palpable by the eighth to tenth weeks.

During pregnancy, the uterus grows by over twenty-fold to accommodate an approximate capacity of up to five liters. The dramatic growth of the uterus during pregnancy is achieved through two mechanisms: hyperplasia, the formation of new cells, occurs in the first half of pregnancy and is followed by hypertrophy or enlargement of those cells during the second half. By the end of pregnancy, the uterus has a thickness of only 5 mm. For perspective, one penny is 1 mm thick; the whole of life is contained in a muscular pouch no thicker than a stack of five pennies. The thinness of the veil that physically separates us from our babies is remarkable because it is the embodiment of strength in resilience.

The birth and postpartum periods are dominated by the incredible power of the uterus. During gestation, the uterus has grown and yet remained flexible while it safely secures the contents inside. Then, remarkably, this same organ completes the work of releasing and expelling not only the baby but the placenta. This is accomplished by a pairing of both power and relaxation, because in order to have the strength, there must be the rest phase. After the birth is done, the uterus completes the process of returning to its pre-pregnant state. Within six short weeks, the work of the previous 40 weeks is undone, the process of involution has occurred, and the uterus is once again tucked deep inside the pelvis.

Uterus. One word, three syllables, six letters, and the throne of power. The dwelling of the spark of life, the radiant source where the work and the magic thrive. The words used to name it are plentiful. No other organ in the human body is capable of such transformation, growth, or strength. In learning and studying the uterus, in being at the side of laboring clients, I have come to be in awe of this deceptively simple muscle. The unseen heroine of the birth process, just below the surface, the epitome of strength in softness. The womb is where the magic of work happens, where physiology and spirituality entwine to create life itself and then bring that life Earthside.