Uterine Inversion

Etiology

Excessive umbilical cord traction with a fundal attachment of the placenta and fundal pressure in the setting of a relaxed uterus are the 2 most common proposed aetiologies for uterine inversion. Other possible risk factors for uterine inversion include rapid labor, invasive placentation, manual removal of placenta, short umbilical cord, use of uterine-relaxing agents, uterine overdistension, fetal macrosomia, nulliparity, placenta previa, connective tissue disorders (Marfan syndrome and Ehlers-Danlos syndrome), and history of uterine inversion in the previous pregnancy. However, in most cases, no risk factors are identified, thus making this condition unpredictable.[2][3][4]

Degrees of Uterine Inversion

• Incomplete: Fundus inverts but does not herniate through the level of the internal os
• Complete: The internal lining of the fundus crosses through the cervical os with no palpable fundus abdominally
• Prolapsed: Entire uterus prolapsing through the cervix with the fundus passing out of the introitus

Classification

• Acute: 24 hours or less after delivery
• Subacute Longer than 24 hours postpartum)
• Chronic: Longer than 1 month postpartum[1][5]

Epidemiology

A uterine inversion is rare, complicating about 1 in 2000 to 1 in 23,000 deliveries. Ironically, most are seen with “low-risk” deliveries. The incidence is 3 times higher in India than in the United States. Uterine inversion has decreased fourfold after the introduction of active management during the third stage.

Pathophysiology

Three possible events explain the pathophysiology of acute uterine inversion:

1. A portion of the uterine wall prolapses through the dilated cervix or indents forward
2. Relaxation of part of the uterine wall
3. Simultaneous downward traction on the fundus leading to the uterine inversion

History and Physical

Uterine inversion is a clinical diagnosis and should be suspected when the fundus is not palpable abdominally. The sudden onset of brisk vaginal bleeding leads to hemodynamic instability in the mother. Traditionally, the shock has been considered disproportionate to blood loss, possibly mediated by parasympathetic stimulation caused by the stretching of tissues. However, careful evaluation of the need for blood transfusion should be made because blood loss is greatly underestimated. The other symptoms are mainly severe lower abdominal pain with a strong bearing down sensation, though most women may not be able to complain due to severe shock. It may occur before or after placental detachment.[1][6]

Evaluation

The diagnosis is often made clinically with a bimanual examination, during which the uterine fundus is palpated in the lower uterine segment or within the vagina. If a clinical examination is equivocal, then an ultrasound can be used to confirm the diagnosis.[7][1][8]

Treatment / Management

Once the diagnosis of uterine inversion is made, immediate intervention to control hemorrhage and restore hemodynamic stability in the mother is required because a delay leads to an increase in the mortality rate appreciably. The following actions should be taken urgently and simultaneously:

• Call for help and call for an anesthesiologist immediately.
• A large-bore cannula achieves hemodynamic stability, and crystalloid and blood are given to combat hypovolemia.
• The recent uterine inversion with the placenta already separated from it may often be replaced by manually pushing up on the fundus with the palm and fingers in the direction of the long axis of the vagina. A delay renders replacement more difficult and increases the risk of hemorrhage.
• If the placenta is still attached, it is usually not removed until fluids are given and uterine-relaxing anesthetics, such as a halogenated inhalation agent, have been administered. Other tocolytic agents, such as magnesium sulfate or beta-mimetic and nitroglycerine, have been used successfully for uterine relaxation and repositioning. Any portion of the inverted uterus prolapsed beyond the vagina is replaced within the vagina.
• After the placenta is removed, steady pressure with the fist is applied to the inverted fundus to push it into the dilated cervix. Alternatively, 2 fingers can be extended rigidly to push the center of the fundus upward. Undue force is not applied to avoid perforation of the uterus with the fingertips. This is followed by the administration of uterotonic agents, which help uterine contraction, thereby preventing the recurrence of the inversion.

An appropriate antibiotic is administered to prevent infection. Other options include hydrostatic reduction and surgical correction if manual repositioning is unsuccessful due to a dense constriction ring.

Hydrostatic reduction: If manual reduction alone is not successful, simple hydrostatic pressure may be of great assistance in pushing the fundus back to its normal anatomical position. Warmed sterile saline is infused into the vagina. The clinician’s hand or a silicone ventouse cup is used as a fluid retainer to generate intravaginal hydrostatic pressure and resultant inversion correction. The bag of fluid should be elevated about 100 to 150 cm above the vagina to guarantee sufficient pressure for insufflation. It also prevents blood loss and prevents the uterus from inverting again. The possible complications of the procedure include infection, failure, and saline embolus.

Surgical options include Huntington and Haultain procedures, laparoscopic-assisted repositioning, and cervical incisions with manual uterine repositioning. The Huntington procedure involves laparotomy by gradually pulling on the round ligaments to restore the uterus to its proper position. If the cervical ring is tight, repositioning may be more easily achieved by incising the ring posteriorly with a vertical incision and manually pushing the fundus. As with manual repositioning, after replacing the fundus, the anesthetic agent used to relax the myometrium is stopped, and uterotonic therapy is administered immediately, followed by the repair of the uterine incision. If these procedures are performed, then pregnancies in the future require a cesarean delivery. If the placenta is not separated from the uterus, then a hysterectomy may be necessary.

Differential Diagnosis

The conditions that cause a lump in the vagina and lead to postpartum collapse need to be excluded. These include:

• Severe atony of the uterus
• Uterovaginal prolapse
• Fibroid polyp
• Neurogenic collapse
• Postpartum collapse
• Retained placenta without inversion
• Coagulopathy

Prognosis

Acute cases can lead to hemorrhagic shock, but prompt management usually mitigates long-term sequelae. It is unknown whether the condition affects future pregnancy prospects, but case reports exist of uncomplicated pregnancies.

Complications

Complications associated with uterine inversion can be due to the condition (primary) or its management (secondary). The condition's complications primarily revolve around hemorrhage and its associated risks, including multi-organ damage, shock, Sheehan syndrome, and hysterectomy). The condition can result in significant, persistent blood loss and tissue necrosis without treatment. Complications accompanying treatment relate to general anesthesia and blood transfusions.