Uterine Involution and the First 40 Days: From “Open” to Closing the Gates

The first 40 days after birth have long held special importance in Traditional Chinese Medicine and many Asian postpartum traditions. In TCM, childbirth represents an enormous expenditure of Blood, Qi and fluids. Immediately after birth, the mother is considered particularly “open” and vulnerable. The goal of postpartum care is to protect, nourish and gradually restore her, sometimes described as “closing the gates.”

Interestingly, this traditional recovery window overlaps closely with one of the most dramatic physical changes happening after birth: uterine involution.

Uterine involution is the process through which the uterus contracts, heals and returns toward its nonpregnant size and state. It begins immediately after delivery of the placenta and continues for approximately six weeks, or roughly the first 40 to 42 days postpartum.

This does not mean uterine involution and the TCM concept of “closing the gates” are the same thing. They come from different medical frameworks. But both recognize something important: birth is not the end of the physical process. It begins an intense period of recovery.

What Happens to the Uterus After Birth?

Immediately after delivery, the uterus still weighs approximately 1,000 grams, or about 2.2 pounds. Strong uterine contractions begin immediately, compressing blood vessels where the placenta separated and helping control postpartum bleeding.

Over the following days and weeks, the uterus undergoes extensive remodeling. The enlarged uterine muscle cells shrink dramatically in size, uterine blood vessels change, the endometrial lining regenerates and the placental site gradually heals.

By approximately one week, the uterus weighs around 500 grams. By about two weeks, it has descended back into the pelvis and normally can no longer be felt through the abdomen. By approximately six weeks, it has decreased to roughly 50 to 100 grams and is approaching its nonpregnant state.

This is a remarkable amount of healing and remodeling taking place in a very short period of time.

Lochia Is Part of This Process

Alongside uterine involution is lochia, the normal postpartum discharge of blood, mucus and uterine tissue.

During the first several days, lochia is generally red and blood-rich. It then usually becomes pink or brown before gradually becoming lighter, yellowish or white. These changes happen as the uterus contracts, the endometrial lining regenerates and the placental site heals. The exact timing varies from woman to woman.

This is important when discussing the traditional idea of “cleansing” after birth. The body does not need a juice cleanse, detox diet or anything designed to force the uterus to empty. Lochia and uterine involution are normal physiological processes.

In TCM, however, “clearing” has a different meaning.

The First Stage: Clear, Recover, Then Rebuild

In Traditional Chinese Medicine, the immediate days after birth are treated differently from the weeks that follow. The mother has experienced major movement and loss of Blood and fluids, lochia is still being discharged, and the body is beginning its transition from pregnancy into recovery.

Traditional postpartum herbal practice therefore includes the concept of supporting the normal movement of Blood and addressing what TCM describes as Blood stasis while also beginning to nourish the depleted mother.

This is the thinking behind FAMMá's first postpartum stage, Cleanse & Recover.

“Cleanse” does not mean fasting, restricting food or forcing the body to detox. It refers to the traditional concept of allowing the early postpartum process to occur before moving into progressively deeper Blood and Qi nourishment.

Certain traditional postpartum formulas and herbs are described in TCM as moving Blood, addressing Blood stasis and supporting Blood after childbirth. As the postpartum period progresses, the emphasis changes toward restoring Blood and Qi, rebuilding strength, deeper nourishment and vitality.

This is why traditional postpartum herbal care is progressive. The herbs appropriate immediately after birth are not necessarily the herbs used throughout all six weeks.

In modern physiology, we describe uterine contraction, vascular remodeling, lochia, endometrial regeneration and placental-site healing. TCM describes this early postpartum period through a different framework involving Blood, Blood stasis, Qi and gradual restoration. The two systems should not be treated as medically interchangeable, but both recognize that the first days after birth are different from the later rebuilding stages.

Breastfeeding and the Shrinking Uterus

There is also a direct physiological connection between breastfeeding and the uterus.

When a baby suckles, the mother's body releases oxytocin. Oxytocin causes the milk-ejection reflex, but it also causes the uterus to contract. This is why many mothers experience noticeable cramps, often called afterpains, while breastfeeding during the first days postpartum.

These contractions are normal and contribute to postpartum uterine contraction and involution.

Breastfeeding is not required for the uterus to involute normally. Mothers who cannot breastfeed or choose not to breastfeed still undergo uterine involution. Breastfeeding simply provides an additional oxytocin stimulus for uterine contraction.

Where Rest and Nutrition Fit In

No particular food, herb or supplement can make the uterus shrink on command. Uterine involution is a physiological process driven primarily by hormonal changes, uterine contraction and tissue remodeling.

But the uterus is not recovering in isolation.

The mother may simultaneously be recovering from blood loss, tissue injury, a vaginal delivery or surgery, hormonal changes, disrupted sleep and the nutritional demands of lactation. Her body requires energy and raw materials for tissue repair, blood formation, immune function and normal metabolism throughout this process.

Adequate calories, protein, carbohydrates, healthy fats, fluids, iron, folate, B vitamins, vitamin C, zinc, copper and other vitamins and minerals all contribute to the larger nutritional environment in which recovery occurs.

This is one reason traditional postpartum diets rely heavily on warm soups, broths, congees, porridges, meat, fish, eggs, grains, vegetables, roots, fruits, fungi and herbs. They allow fluid, protein, carbohydrates, fats, minerals and other nutrients to be delivered together in foods that are easy to eat while the mother rests.

Rest matters too. The first 40 days should not be viewed as a race to exercise harder, lose pregnancy weight, return to work or prove that the mother is “back to normal.” Her body is actively healing.

Who Is Watching the Mother During These 40 Days?

Uterine involution is not something a mother should be expected to diagnose herself. Healthcare professionals can assess uterine recovery, bleeding, infection, wounds, blood pressure, breastfeeding, mental health and other aspects of postpartum healing.

Unfortunately, postpartum care in the United States has historically centered around a single postpartum visit approximately four to six weeks after birth. ACOG itself has recognized the limitations of this model and now recommends postpartum care as an ongoing process, beginning with contact with an obstetric provider within the first three weeks rather than waiting for one traditional six-week appointment.

The World Health Organization recommends even earlier and more frequent postnatal contact, including care within the first 24 hours, between 48 and 72 hours, between days 7 and 14, and around six weeks. Maternal assessment during postpartum care includes bleeding and uterine involution.

Other countries also structure postpartum follow-up differently. Japan commonly incorporates maternal checks around two weeks and one month postpartum, while Taiwan's current postpartum program recommends maternal assessments around one to two weeks and again around six to eight weeks. These visits can address physical recovery, breastfeeding and maternal mental health, with pelvic examination or ultrasound used when clinically appropriate.

The important point is not that every mother needs an ultrasound every two weeks. She does not.

It is that much of uterine involution is happening long before the traditional American six-week postpartum appointment.

Mothers Should Know What to Watch For

A mother should not be responsible for determining whether her uterus weighs the “right” amount, whether her fundal height is normal or whether she has properly involuted. Those are clinical assessments.

But because so much recovery happens at home, mothers and their families should understand what normal recovery generally looks like and recognize when something appears wrong.

Bleeding should generally trend downward over time. Lochia normally changes in color and becomes lighter. Cramping and afterpains are common, particularly during the early days and while breastfeeding.

Heavy or suddenly increasing bleeding, foul-smelling discharge, fever or chills, worsening abdominal or pelvic pain, severe weakness, dizziness or fainting require medical attention. Abnormal uterine involution, called subinvolution, can occur with problems including retained placental tissue or uterine infection.

Knowing these signs is not asking mothers to become their own doctors. It gives them the information necessary to recognize when they need one.

Why the First 40 Days Matter

The traditional 40-day recovery period is not scientifically validated simply because uterine involution also takes approximately six weeks. Those are two different frameworks, and it is important not to confuse correlation with proof.

But the overlap is difficult to ignore.

For generations, postpartum traditions have protected mothers for approximately a month or longer with rest, warmth, prepared food, family support and progressive nourishment. Modern physiology now gives us a remarkable view of just how much is actually happening inside the body during approximately that same period.

The uterus is shrinking from around 1,000 grams toward approximately 50 to 100 grams. The placental site is healing. The uterine lining is regenerating. Lochia is changing. Blood volume and hormones are shifting. Tissues are repairing. Lactation may be establishing. Sleep is disrupted. And the mother is simultaneously learning to care for a newborn.

The body does not simply deliver a baby and become “normal” again.

Closing the Gates

The TCM concept of “closing the gates” should not be interpreted literally as the uterus closing. It describes something broader: protecting and restoring the mother after the tremendous opening, expenditure and transition of childbirth.

The earliest stage includes clearing and recovery. Then comes restoration. Then rebuilding, strengthening, nourishment and vitality.

That is also the thinking behind FAMMá's six-week TCM-inspired postpartum recovery progression:

Cleanse & Recover → Restore → Rebuild → Strengthen → Nourish → Vitality.

The first 40 days are not the end of postpartum. Healing, breastfeeding, sleep disruption, hormonal adjustment and the transition into motherhood can continue far beyond six weeks.

But these first 40 to 42 days represent an extraordinary early window of physical recovery.

The baby has been born.

The mother's recovery has just begun.