Female - Round Ligament of Uterus

1. Overview

The round ligament of the uterus is a fibromuscular cord that extends from the uterus to the labia majora, playing a crucial role in maintaining the anteverted position of the uterus. It is a remnant of the embryonic gubernaculum and is classified as one of the major supporting ligaments of the female reproductive organs. Though not directly involved in reproduction, the round ligament contributes to the mechanical stability of the uterus, particularly during pregnancy.

2. Location

The round ligament originates at the uterine horns, near the junction where the uterus and fallopian tubes meet (anterior to and below the origin of the fallopian tubes). From there, it passes laterally through the layers of the broad ligament, exits the pelvis via the deep inguinal ring, traverses the inguinal canal, and finally inserts into the subcutaneous tissue of the labia majora and mons pubis.

3. Structure

The round ligament is approximately 10–12 cm long and consists of:

• Fibrous connective tissue: Provides tensile strength and continuity with the uterine wall.

• Bundles of smooth muscle: Allow limited contractile function in response to hormonal changes.

• Blood vessels and nerves: Accompany the ligament through the inguinal canal; vascular supply is from the uterine and ovarian arteries.

• Peritoneal covering: As it lies within the broad ligament, the round ligament is enclosed by a layer of peritoneum.

Embryologically, it is the female equivalent of the gubernaculum testis in males and guides the descent of the ovaries during development.

4. Function

The round ligament primarily functions to:

• Maintain the anteverted position of the uterus: By anchoring the uterus anteriorly toward the labia majora, it helps prevent posterior displacement (retroversion).

• Stabilize the uterus during movement: Acts like a tether to limit excessive mobility, particularly during physical activity or changes in posture.

• Adapt to uterine growth during pregnancy: Stretches significantly to accommodate the enlarging uterus and maintain orientation.

5. Physiological Role(s)

Although it does not play a hormonal or reproductive role directly, the round ligament contributes physiologically by:

• Mechanical support: Helps preserve uterine positioning, crucial for optimal alignment of the uterus, fallopian tubes, and vagina for conception and implantation.

• Hormonal responsiveness: The smooth muscle fibers within the ligament may respond to hormonal changes (especially during pregnancy), contributing to ligament relaxation and discomfort.

• Pregnancy adaptation: As the uterus grows, the round ligaments stretch and elongate. This stretching can lead to sensations known as “round ligament pain,” a common feature in the second trimester.

6. Clinical Significance

The round ligament is clinically significant in several contexts:

• Round ligament pain: A common cause of lower abdominal or groin pain in pregnant women, especially during the second trimester. It results from stretching, spasms, or irritation of the ligament as the uterus enlarges. Typically self-limiting but can mimic other acute abdominal conditions.

• Endometriosis of the round ligament: Endometrial tissue can implant on or within the round ligament, often presenting as cyclic inguinal pain, sometimes mistaken for a hernia.

• Inguinal hernias: Although rare in females, the round ligament passes through the inguinal canal, a potential site for indirect inguinal hernias, especially if the canal remains patent (e.g., canal of Nuck).

• Surgical relevance: The round ligament is identified and sometimes transected during pelvic surgeries such as hysterectomy or laparoscopic procedures for better access to the uterus and adnexa.

• Round ligament varicosities: Dilated veins around the ligament during pregnancy may resemble inguinal hernias but typically resolve postpartum. Proper diagnosis via ultrasound avoids unnecessary surgery.

Understanding the anatomy and function of the round ligament is essential in obstetrics and gynecology, particularly for diagnosing pregnancy-related pelvic pain and differentiating benign ligament issues from surgical emergencies.