The term uterine inversion is a condition in which the fundus of the uterus —the end of the uterus opposite cervix— drops down through the cavity of the uterus and through the cervix so that the uterus is now hanging inside out. This is an extremely rare complication of vaginal delivery, but when it occurs it’s a life-threatening obstetric emergency. Uterine inversion is subcategorized into partial inversion (also called incomplete inversion) and complete inversion. In partial uterine inversion, the fundus of the uterus falls through the cervix but does not reach the introitus (the opening of the vagina). In complete uterine inversion, the fundus drops through the introitus.
One possible cause of uterine inversion is difficulty during active management of the third stage of labor, especially in cases of placenta accreta. Just to remind you, we discussed the third stage of labor in our recent post about the basics of labor and delivery. The third stage of labor begins with the completion of the birth of the baby and ends with the delivery of the placenta. There are two approaches to managing the third stage of labor: physiological management and active management. In physiological management, the placenta is delivered by the mother’s effort without medications or cord traction. This approach allows the mother to deliver the placenta on her own, but it may take longer than the active management approach. Active management involves the obstetrician or midwife assisting in the delivery of the placenta. A dose of oxytocin is administered by intramuscular injection to help the uterus contract and expel the placenta.
The clinician also may apply careful traction on the umbilical cord to pull the placenta out of the uterus and vagina. In doing this, however, sometimes it can be difficult to feel how much tension is necessary to get the placenta out, and in cases of placenta accreta, pulling the cord lightly often will not get the placenta out. Just to remind you of our discussion on placental complications, placenta accreta is a situation in which the placenta is wedged too deeply into the uterus. It penetrates all the way through the endometrium and sometimes into the underlying myometrium, the muscular layer of the uterus. If the placenta is attached this way, and if it’s attached at the fundus, then pulling hard on the umbilical cord in an attempt to pull the placenta out can pull the fundus down, causing uterine inversion.
This typical setting in which uterine inversion presents is a major postpartum hemorrhage. Causes of postpartum hemorrhage include uterine atony (failure of the uterus to contract after delivery), trauma, such as a perineal tear or laceration (tear or cut of muscle between the vagina and anus), and retained fragments of the placenta. Postpartum hemorrhage bad enough to provoke uterine inversion may also cause maternal shock.
Obstetricians and midwives may be able to detect partial uterine inversion by simply examining the pelvis and abdomen with their hands. In cases of complete uterine inversion, the inner fundus of the uterus may be visible at the introitus, the opening of the vagina.
As for managing uterine inversion, there generally are three options: the Johnson maneuver, hydrostatic methods, and surgical intervention. The Johnson maneuver should be the first intervention that the doctor attempts. This maneuver involves using one’s hand to push the fundus of the uterus back into the abdomen, and to its appropriate position. To get the fundus as far as it needs to go, most of the doctor’s (or midwife’s) forearm may need to go into the vagina. The doctor or midwife then must hold the uterus in place for a long time, usually several minutes, while the woman is given medications, such as oxytocin, which causes the uterus to contract, which can help tighten the uterus and its various ligaments, anchoring the organ back into its correct position.
As you may imagine, the Johnson maneuver does not always work, so when it fails the next step is to implement hydrostatic interventions. Generally, this means forcing fluid into the vagina, filling it up, causing it to push the uterine fundus upward, so the pressure of the fluid takes the place of the doctor’s hand. To make this work, the healthcare team must create a tight seal around the vagina and the tube through which fluid is being pumped into it. If both the Johnson maneuver and hydrostatic methods fail, this is when surgery is needed. Generally, this is done by way of a laparotomy, meaning that the obstetrician makes an incision through the abdomen. While all of this is being done, the patient may require various lifesaving methods, including fluid resuscitation (intravenous fluids are given to raise blood volume and pressure), transfusion of blood products, and advanced cardiac life support.