• Uterine inversion is a potentially fatal complication of childbirth.
• Uterine inversion means the placenta fails to detach from the uterine wall, and pulls the uterus inside-out as it exits.
• Treatment options depend on the severity, but could include reinserting the uterus by hand, abdominal surgery or emergency hysterectomy.

Uterine inversion is a potentially life-threatening complication of childbirth. Normally, the placenta detaches from the uterus and exits the vagina around half an hour after the baby is delivered. Uterine inversion means the placenta remains attached, and its exit pulls the uterus inside-out.

In most cases, the doctor can manually detach the placenta and push the uterus back into position. Occasionally, abdominal surgery is required to reposition the uterus.

The rate of uterine inversion is estimated from one in 2,000 to one in several hundred thousand labours. Estimates vary widely - depending on the study. The mother’s survival rate is about 85 per cent. The cause of death includes massive bleeding (haemorrhage) and shock.

The uterus is the muscular organ that nourishes and supports the growing embryo (see image). Its average size is approximately 5 cm wide by 7 cm long (approximately 2 in by 3 in) when a female is not pregnant. It has three sections. The portion of the uterus superior to the opening of the uterine tubes is called the fundus. The middle section of the uterus is called the body of uterus (or corpus). The cervix is the narrow inferior portion of the uterus that projects into the vagina. The cervix produces mucus secretions that become thin and stringy under the influence of high systemic plasma estrogen concentrations, and these secretions can facilitate sperm movement through the reproductive tract.

Ovaries, Uterine Tubes, and Uterus

Figure 27.14 Ovaries, Uterine Tubes, and Uterus This anterior view shows the relationship of the ovaries, uterine tubes (oviducts), and uterus. Sperm enter through the vagina, and fertilization of an ovulated oocyte usually occurs in the distal uterine tube. From left to right, LM × 400, LM × 20. (Micrographs provided by the Regents of University of Michigan Medical School © 2012)

This anterior view shows the relationship of the ovaries, uterine tubes (oviducts), and uterus. Sperm enter through the vagina, and fertilization of an ovulated oocyte usually occurs in the distal uterine tube. From left to right, LM × 400, LM × 20. (Micrographs provided by the Regents of University of Michigan Medical School © 2012)

Several ligaments maintain the position of the uterus within the abdominopelvic cavity. The broad ligament is a fold of peritoneum that serves as a primary support for the uterus, extending laterally from both sides of the uterus and attaching it to the pelvic wall. The round ligament attaches to the uterus near the uterine tubes, and extends to the labia majora. Finally, the uterosacral ligament stabilizes the uterus posteriorly by its connection from the cervix to the pelvic wall.

The wall of the uterus is made up of three layers. The most superficial layer is the serous membrane, or perimetrium, which consists of epithelial tissue that covers the exterior portion of the uterus. The middle layer, or myometrium, is a thick layer of smooth muscle responsible for uterine contractions. Most of the uterus is myometrial tissue, and the muscle fibers run horizontally, vertically, and diagonally, allowing the powerful contractions that occur during labor and the less powerful contractions (or cramps) that help to expel menstrual blood during a woman’s period. Anteriorly directed myometrial contractions also occur near the time of ovulation, and are thought to possibly facilitate the transport of sperm through the female reproductive tract.

The innermost layer of the uterus is called the endometrium. The endometrium contains a connective tissue lining, the lamina propria, which is covered by epithelial tissue that lines the lumen. Structurally, the endometrium consists of two layers: the stratum basalis and the stratum functionalis (the basal and functional layers). The stratum basalis layer is part of the lamina propria and is adjacent to the myometrium; this layer does not shed during menses. In contrast, the thicker stratum functionalis layer contains the glandular portion of the lamina propria and the endothelial tissue that lines the uterine lumen. It is the stratum functionalis that grows and thickens in response to increased levels of estrogen and progesterone. In the luteal phase of the menstrual cycle, special branches off of the uterine artery called spiral arteries supply the thickened stratum functionalis. This inner functional layer provides the proper site of implantation for the fertilized egg, and—should fertilization not occur—it is only the stratum functionalis layer of the endometrium that sheds during menstruation.

Recall that during the follicular phase of the ovarian cycle, the tertiary follicles are growing and secreting estrogen. At the same time, the stratum functionalis of the endometrium is thickening to prepare for a potential implantation. The post-ovulatory increase in progesterone, which characterizes the luteal phase, is key for maintaining a thick stratum functionalis. As long as a functional corpus luteum is present in the ovary, the endometrial lining is prepared for implantation. Indeed, if an embryo implants, signals are sent to the corpus luteum to continue secreting progesterone to maintain the endometrium, and thus maintain the pregnancy. If an embryo does not implant, no signal is sent to the corpus luteum and it degrades, ceasing progesterone production and ending the luteal phase. Without progesterone, the endometrium thins and, under the influence of prostaglandins, the spiral arteries of the endometrium constrict and rupture, preventing oxygenated blood from reaching the endometrial tissue. As a result, endometrial tissue dies and blood, pieces of the endometrial tissue, and white blood cells are shed through the vagina during menstruation, or the menses. The first menses after puberty, called menarche, can occur either before or after the first ovulation.

If the oocyte is successfully fertilized, the resulting zygote will begin to divide into two cells, then four, and so on, as it makes its way through the uterine tube and into the uterus. There, it will implant and continue to grow. If the egg is not fertilized, it will simply degrade—either in the uterine tube or in the uterus, where it may be shed with the next menstrual period.

Female Reproductive System

Figure 27.9 Female Reproductive System The major organs of the female reproductive system are located inside the pelvic cavity.

The major organs of the female reproductive system are located inside the pelvic cavity.

Grades of inversion

Uterine inversion is graded by its severity. This includes:

• Incomplete inversion - the top of the uterus (fundus) has collapsed, but the uterus hasn’t come through the cervix.
• Complete inversion - the uterus is inside-out and coming out through the cervix.
• Prolapsed inversion - the fundus of the uterus is coming out of the vagina.
• Total inversion - both the uterus and vagina protrude inside-out (this occurs more commonly in cases of cancer than childbirth).

Risk factors

Some of the factors associated with an increased risk of uterine inversion include:

• Prior deliveries.
• Long labour (more than 24 hours).
• Use of the muscle relaxant magnesium sulphate during labour.
• Short umbilical cord.
• Pulling too hard on the umbilical cord to hasten delivery of the placenta, particularly if the placenta is attached to the fundus.
• Placenta accreta (the placenta has invaded too deeply into the uterine wall).
• Congenital abnormalities or weaknesses of the uterus.

Prompt diagnosis is crucial and possibly lifesaving. Some of the signs of uterine inversion could include:

• The uterus protrudes from the vagina.
• The fundus doesn’t seem to be in its proper position when the doctor palpates (feels) the mother’s abdomen.
• The mother experiences greater than normal blood loss.
• The mother’s blood pressure drops (hypotension).
• The mother shows signs of shock (blood loss).
• Scans (such as ultrasound or MRI) may be used in some cases to confirm the diagnosis.

Treatment options vary, depending on the individual circumstances and the preferences of the hospital staff, but could include:

• Attempts to reinsert the uterus by hand.
• Administration of drugs to soften the uterus during reinsertion.
• Flushing the vagina with saline solution so that the water pressure ‘inflates’ the uterus and props it back into position (hydrostatic correction).
• Manual reinsertion of the uterus while the woman is under general anaesthetic.
• Abdominal surgery to reposition the uterus if all other attempts to reinsert it have failed.
• Antibiotics to reduce the risk of infection.
• Intravenous liquids.
• Blood transfusion.
• Intravenous administration of oxytocin to trigger contractions and stop the uterus from inverting again.
• Emergency hysterectomy (surgical removal of the uterus) in extreme cases where the risk of maternal death is high.
• Close monitoring in intensive care for a few days, if necessary.

Whether the placenta is detached before or after the repositioning of the uterus depends on the circumstances and the preferences of the hospital staff. For example, the placenta may be so engorged with blood that it’s too big to push back through the cervix. This means that either the placenta is manually detached, or else the uterus (and attached placenta) is repositioned surgically. Some doctors believe that removing the placenta prior to repositioning the uterus increases the risk of haemorrhage. In this case, the treatment option would be surgery.

Increased risk for subsequent pregnancies

A woman who has experienced uterine inversion is at risk of it happening again in subsequent pregnancies. If you change doctors, make sure you tell them about your complication, so they can include precautionary measures in the labour ward. For example, your doctor may want to have appropriate equipment on hand, such as anaesthesia.

Things to remember

• Uterine inversion is a potentially fatal complication of childbirth.
• Uterine inversion means the placenta fails to detach from the uterine wall, and pulls the uterus inside-out as it exits.
• Treatment options depend on the severity, but could include reinserting the uterus by hand, abdominal surgery or emergency hysterectomy.