From the Guidelines
The graph of uterine involution is characterized by a rapid decline in uterine size during the first week postpartum, followed by a more gradual decrease over the next 6-8 weeks, with the uterus returning to its pre-pregnancy size of about 60-100 grams 1.
Uterine Involution Process
The process of uterine involution is complex and involves the withdrawal of placental estrogens and progesterone, reduction of myometrial blood flow, and the return of pregnancy-regulated genes to pre-pregnancy values 1.
- The y-axis of the graph typically represents uterine size, measured by fundal height in centimeters above the symphysis pubis or by weight in grams.
- The x-axis shows time postpartum in days or weeks.
- The curve on the graph demonstrates a rapid decline in uterine size during the first week postpartum, with the uterus decreasing to approximately 500 grams by the end of the first week.
- The rate of involution then slows, creating a more gradual slope on the graph over the remaining weeks.
Clinical Significance
Healthcare providers use the graph of uterine involution as a reference to ensure normal postpartum uterine regression, as delayed involution may indicate complications such as retained placental fragments or postpartum infection 1.
- By day 10, the uterus typically descends into the pelvis and is no longer palpable abdominally.
- The involution process occurs through autolysis (self-digestion of excess tissue) and contraction of smooth muscle fibers.
- Understanding the graph of uterine involution is essential for healthcare providers to monitor postpartum recovery and identify potential complications early on.
From the Research
Uterine Involution Graph
The graph of uterine involution can be described as follows:
- Uterine involution is rapid during the first week after childbirth and then slows down 2
- By day 28 postpartum, the dimensions of the uterus have returned to the upper limit for the non-pregnant uterus 2
- The uterus reassumes nongravid dimensions by 6 to 8 postpartum weeks 3
- There is considerable variability in the pattern of uterine involution experienced by women who have a normal puerperium 4
Key Findings
- The size of the uterus and the uterine cavity can be measured using abdominal ultrasound 2
- Uterine contractions can cause instability of the transverse dimension, making it difficult to measure 3
- Increasing maternal parity is associated with slightly but significantly larger uterine dimensions up to 4 weeks postpartum 3
- The measurement of the distance between the symphysis pubis and the uterine fundus (S-FD) has a low specificity for identifying normal uterine involution 4
Uterine Involution Process
- Uterine involution involves the involution of vessels and myometrium 5
- The myometrium dramatically enlarges due to gestational hyperplasia and hypertrophy of myocytes, caused by hormonal influences of the fetal adrenal cortex and the placenta 5
- After delivery, uterine weight drops rapidly, with physiologic involution of myometrium associated with massive destruction of myometrial tissue 5
- The role of stem cells in uterine involution is poorly understood, but it is thought to involve the regeneration of the endometrium and the return of the myometrium to the pre-gravid state 6