Uterine Defect Repair in an Ongoing Pregnancy

Eyal Krispin

Michael A. Belfort

Alireza A. Shamshirsaz

GENERAL PRINCIPLES

Definition

Uterine rupture is defined as complete disruption of the uterine wall and overlying peritoneum, exposing the interior of the uterine cavity to the abdominal cavity. This is a rather rare event that usually, but not always, occurs during labor in a previously scarred uterus. Spontaneous uterine rupture in an unscarred uterus is most commonly seen in protracted labor with absolute fetal-pelvic disproportion. The most frequently reported prior uterine surgery is cesarean section; however, other procedures that potentially disrupt the integrity of the uterine wall such as myomectomy, fetal surgery, and uterine perforation may also lead to uterine rupture (1).

Uterine rupture during pregnancy is an obstetric emergency; it endangers both the mother and the fetus. The typical clinical presentation of uterine rupture during labor includes abdominal pain, vaginal bleeding, and nonreassuring fetal heart rate monitoring. Physical examination may reveal an abnormal contour of the gravid uterus, vaginal bleeding, and loss of station of the presenting part. An ultrasound scan demonstrating a noncontinuous uterine wall and/or fetal parts outside of the uterine cavity associated with free fluid in the abdomen will strongly support the diagnosis.

Uterine rupture should be treated surgically, and following laparotomy and extraction of the neonate, debridement of the defect and a layered closure should be possible in most cases, although frequently a hysterectomy may be required (2).

Uterine dehiscence describes a milder degree of disruption in the integrity of the uterine wall as compared to a complete rupture and is usually described as a myometrial defect with intact visceral peritoneum. There are similar risk factors as for uterine rupture. The clinical presentation is usually more subtle, and some cases are completely asymptomatic only being discovered at the time of an elective laparotomy (i.e., cesarean delivery). Acute dehiscence of a uterine scar should be suspected when a patient in labor with a prior cesarean scar complains of worsening lower abdominal tenderness, but often the first sign of dehiscence and/or rupture is sudden onset fetal heart rate decompensation. Repair of a uterine dehiscence noted at the time of cesarean delivery is similar to that used to close any hysterotomy, and the defect rarely requires debridement.
Scar disruption is rarely diagnosed outside of the context of active labor. Published reports have mainly focused on patients who have had a prior history of major uterine wall disruption or injury (3). Most commonly, the previous injury was in the uterine fundus (i.e., upper segment classical uterine incision), a cornual ectopic pregnancy with major resection, or a prior uterine rupture. The coexistence of uterine disruption and an ongoing pregnancy with a pre-viable fetus poses both ethical dilemmas and surgical challenges. In this chapter, we aim to address the rare diagnosis of interrupted uterine wall during the first and second trimesters of an otherwise normal pregnancy.

Physical Examination

Vital signs: Uterine disruption (even dehiscence) always has the risk of sudden and extensive bleeding. In all cases, evaluation of the maternal vital signs and examination for evidence of incipient or ongoing blood loss are crucial.
Abdominal examination
- Abnormal appearance of the abdomen and uterine silhouette is often seen. This may be as little as an abnormal bulging or asymmetry to an obvious hourglass shaped uterus indicating that the portion above the disruption has retracted away from the portion below (classically seen in a term patient with a large baby). Depending on the degree and duration of the disruption, the fetus (alive or dead) still be inside the uterus, partially extruded, or completely free-floating in the abdomen.
- Palpation of the uterus might add further information. With an extensive disruption in a nonlaboring patient, the amniotic sac and parts of the fetus may protrude through the disrupted wall allowing visualization of the shape and movement of the small parts of the fetus.
Pelvic examination: Speculum inspection to rule out vaginal bleeding and premature rupture of membranes.

Differential Diagnosis

Partial or segmental uterine contraction causing the impression of a protruding fetal part in the lower segment. This can happen with a very thin maternal abdominal wall.
Ectopic pregnancy with peritoneal implantation and an abdominal pregnancy.
Heterotopic pregnancy having the ectopic within the uterine wall scar or peritoneum.
Ovarian or para-ovarian cyst that is located adjacent to the uterine wall.
Hydrosalpinx.
Necrotizing leiomyoma.

Nonoperative Management

When uterine disruption is diagnosed in a stable pregnant patient who is not currently bleeding, management decisions can be predicated on a number of factors including (but not limited to) the gestational age, the viability of the pregnancy, genetic screening if available, the perceived maternal risk based on location and size of the disruption, local facilities for managing emergency bleeding, the experience and expertise of the management team, and the desire of the family for the current and future pregnancies.
In all stable patients diagnosed with disrupted uterine wall during the first and second trimesters (within legal constraints), termination of the pregnancy should be discussed. The patient and family must be made aware of the significant risks to maternal and fetal health posed by continuing the pregnancy in the face of such pathology (4). The major concern is hemorrhage, and although there may be no current bleeding, or the bleeding may be indolent causing only chronic anemia, the risk of sudden exsanguination, should the disruption extend and injure large blood vessels (i.e., uterine arteries and veins), is ever present.
In terms of obstetric symptoms, late second and third trimester pregnancies complicated by disruption of the uterine wall are commonly associated with premature contractions, premature rupture of membranes, preterm birth, and stillbirth.
When patients decline termination of pregnancy despite a thorough explanation of the related complications and risks, close observation must be instituted and the pregnancy delivered as soon as it is deemed safe for both mother and baby. The patient should be admitted to a tertiary hospital with a level IV neonatal intensive care unit (NICU). The patient should be instructed to report any abdominal discomfort, decreased fetal movement, and vaginal loss of fluid. Vital signs should be followed closely to warn of hemodynamic instability. In viable pregnancies, bi-weekly biophysical profile is recommended and daily nonstress tests should be considered after 26 weeks of gestation. Antenatal steroids and MgSO₄ for neuroprotection should be instituted per unit protocol once the patient reaches a predetermined gestational age compatible with fetal viability. Cesarean delivery should be recommended following 32 weeks of gestation. Patient’s opinions and wishes regarding repair of the defect, bilateral tubal ligation, and cesarean hysterectomy should be discussed.

IMAGING AND OTHER DIAGNOSTICS

Ultrasound (Figures 3.11.1 and 3.11.2)
- In most cases, the uterine wall disruption is first suspected during a routine obstetric ultrasound: either at the first-trimester nuchal translucency screening scan or at a first-trimester or second-trimester anatomical scan.
- The location and size of the defect should be documented. Any protuberance of the amniotic sac should be evaluated and described.
Magnetic resonance imaging (MRI) (Figures 3.11.3 and 3.11.4)
- MRI is indicated whenever uterine wall disruption during pregnancy is suspected.
- MRI will enable a better definition of the location of the lesion and its anatomic relationships (in 3Ds) to nearby vessels and organs. Volumetric analyses of the lesion are possible, and there is a better resolution of the affected uterine layers.
- MRI is important to improve the ability of the team to gain a better understanding of the ramifications of either expectant or surgical management and to aid in the planning of any potential surgery.

PREOPERATIVE PLANNING

Recent advances in fetal surgery have shown that it is possible to create a hysterotomy and repair it in an ongoing pregnancy. This has raised the potential for elective repair of a suitably located uterine wall defect during the second trimester of an ongoing pregnancy. This might be a consideration in the patient who declines termination of the pregnancy and who intends to continue the pregnancy regardless of the risk to herself. It is possible that in this select group of patients with a
high risk of spontaneous rupture, surgical repair of the defect may be a safer option than expectant management.

Figure 3.11.1. Transabdominal ultrasound image at 19 weeks of gestation demonstrating an area of thin uterine wall in the fundus that extends few centimeters into the placental bed.

Figure 3.11.2. Transabdominal ultrasound image at 19 weeks of gestation demonstrating an area of thin uterine wall measuring 0.18 cm.

Figure 3.11.3. Placental MRI T2 sequence demonstrating a generalized fundal thinning. The fundal margin of the placenta lies just under a portion of this thinning, particularly on the right lateral fundal aspect. This appearance can be seen with the myometrial window. MRI, magnetic resonance imaging.

The patient should have an ethics consultation by an independent ethics professional, and it should be documented that she is fully cognizant and conversant of the risks involved in both expectant management and surgical repair. A Fetal Therapy Board (or equivalent oversight committee) should evaluate the case and give approval.
Preoperative assessment involves a detailed evaluation of the patient’s general health and anesthetic risk, as well as assessment of the feasibility for surgical correction of the defect with consideration of the potential complications for both the mother and the fetus.
Once the decision for surgery is made, decisions regarding the surgical approach (open vs. laparoscopic) and type of repair (excision and primary closure vs. imbrication and buttressing with a Gortex patch) need to be made. The patient should give informed written consent to the primary and alternate approaches depending on the intraoperative findings. She should also consent to abandonment of the procedure, delivery of the pregnancy, and hysterectomy if deemed necessary during the attempted repair.
Excision and primary closure of the uterine wall are likely to be challenging and pose higher risk than imbrication and buttressing with a patch because of the higher potential for bleeding and significant membrane separation associated with surgical resection and repair of myometrial tissue.
- Any attempt at repair will be dependent on the size of the lesion, the volume of the amniotic sac protruding through the defect, and the proximity of the defect to the placenta. If possible, there should be an attempt at the preservation of membrane integrity.
- Whenever there is a significant protuberance of the amniotic sac, amnioreduction should be performed before repair to reduce internal fluid pressure during the repair.

SURGICAL MANAGEMENT

At this time, the surgical correction of a uterine wall defect during an ongoing pregnancy should be considered experimental and a high-risk proposition for both the mother and fetus.

In our opinion, this surgery should only be offered in a facility that has the appropriate primary and support services and a team with experience and expertise in human uterine surgery during pregnancy. This is most commonly a fetal surgery team that has performed hysterotomy-based fetal surgery.

Figure 3.11.4. Placental MRI T1 sequence demonstrating a generalized fundal thinning. The fundal margin of the placenta lies just under a portion of this thinning, particularly on the right lateral fundal aspect. This appearance can be seen with the myometrial window. MRI, magnetic resonance imaging.

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