Umbilical Cord Occlusion Of Complicated Monochorionic Twins:
Information For Healthcare Professionals

Monochorionic twins may present with unique and challenging complications. Because placental vascular anastomoses are present in virtually all monochorionic placentas, compromise to the health of one fetus may adversely affect the health of the co-twin. In particular, spontaneous demise of one twin may result in neurological damage (30% of the time) or death (40% of the time) of the co-twin. These complications are averted by severing the vascular links between the fetuses. As a corollary, selective reduction of one of the fetuses through KCL injection is unwarranted, as this would result in demise of both twins.

In 1994, Quintero et al described the first successful treatment of a patient with TRAP sequence by performing percutaneous umbilical cord ligation (UCL). Since then, this and other modalities of umbilical cord occlusion (UCO) have been developed. The following clinical scenarios constitute indications for UCO in complicated monochorionic twins.

Acardiac twin

Acardiac twins occur in 1:35,000 pregnancies. The syndrome results from reverse perfusion of one twin by a hemodynamically advantaged twin. The acronym TRAP sequence, used to designate the condition, stands for twin reverse arterial perfusion syndrome. The low oxygen content of the blood perfusing the twin is responsible for a set of characteristic anomalies, such as absence of the head, absent or rudimentary heart, and hydrops among others. These anomalies are incompatible with life. Acardiac twin pregnancies have a 50-75% risk of pregnancy loss due to cardiac overload of the pump twin, which results in polyhydramnios and preterm delivery or miscarriage, or in death of the pump twin from heart failure.

Anencephaly

Anencephaly occurs in 1:1000 births. It is a uniformly lethal condition resulting from lack of closure of the neural tube in its anterior portion. Anencephalic fetuses may have difficulty swallowing due to neurological dysfunction. This can lead to polyhydramnios and premature birth or miscarriage. Spontaneous intrauterine demise of anencephalic fetuses occurs in 30-50% of cases. An anencephalic twin may compromise the outcome of the normal co-twin either from accumulation of amniotic fluid and preterm labor, or from spontaneous demise.

Stage III & IV TTTS

Monochorionic twin gestations may be structurally normal, but one of the fetuses may be at an increased risk of dying spontaneously in the uterus due to a functional condition. Common examples include Stage III or Stage IV twin-twin transfusion syndrome, selective severe intrauterine growth retardation and monoamniotic twins with cord entanglement. Hydropic fetuses are an increased risk of dying in utero . Aside from treatable causes such as Rh-sensitization, the overall prognosis for these fetuses is extremely poor. Hydrops may result from severe heart disease, heart failure, or other forms of hemodynamic compromise. Pulsed Doppler velocimetry allows characterization of fetuses with severe hemodynamic compromise to predict the likelihood of spontaneous fetal death. A hydropic twin with hemodynamic signs of impending death may compromise the outcome of the pregnancy, since the spontaneous death of one twin can cause either death or neurological damage to the normal co-twin.

PROM of the presenting twin

Monochorionic twins with previable spontaneous rupture of membranes (PROM) of the presenting twin (twin A), are at risk of loosing the entire pregnancy. Expectant management of these patients typically results in delivery of 90% of patients within 30 days of PROM. If PROM occurs prior to 20-22 weeks, the likelihood of survival for either twin is small. In addition, maternal infectious morbidity may be significant, requiring intensive care management, possible hysterectomy or death. Preliminary data shows that selective reduction of twin A via umbilical cord occlusion may effectively prolong the pregnancy beyond viability and increase the likelihood of a successful outcome for twin B.

Monoamniotic Twins at risk of cord entanglement

Monoamniotic twins represent 1-2% of all twins. The mortality rate for monoamniotic twins is significantly higher than for any other twin group, as high as 50-62%. Entanglement of the umbilical cords of the fetuses with subsequent death of one or both twins accounts for most of the fetal deaths. Congenital anomalies, which are present in 15-20% of cases, and preterm labor account for another significant proportion of fetal demises. The particular combination of cord entanglement and congenital anomalies represent a significant challenge for the management of these patients.

Cord entanglement results from the free movement of the fetuses within the amniotic cavity. It has been found in 40-70% of monoamniotic twins. The cords may be knotted, or simply intertwined. Knotting of a single umbilical cord, as occurs in singleton pregnancies, has also been seen. Although Wharton's jelly is somewhat protective of the umbilical cords, cessation of blood flow to either of the fetuses may occur if the degree of knotting is significant enough to occlude the vessels.

Pregnancies may be lost due to cord entanglement or to the specific hemodynamic challenges imposed on the healthier of the twins.

Ligation of the cord eliminates the communication between the fetuses and prevents any hemodynamic adverse effects on the co-twin. However, it does not prevent demise from cord entanglement. Transection of the umbilical cord eliminates the weight behind one of the cords and thus any possibility of further tightening of the knot.

Non-lethal severe anomaly

Monochorionic twins may also present with a non-lethal severe anomaly of one of the twins.

In these cases, the anomaly is not necessarily lethal in utero, but may be associated with neonatal demise or a significantly decreased quality of life. This situation may create a significant dilemma for some parents, who may choose to discontinue the entire pregnancy because of the presence of the anomalous twin. Alternatively, they may wish to selectively reduce the anomalous twin and attempt to carry the healthy twin to viability. Because of the presence of placental vascular anastomoses, selective reduction of the anomalous twin requires unlinking the circulations of both fetuses either at the level of the placenta or at the level of the umbilical cord. Common examples include spina bifida, hypoplastic left heart syndrome, bladder outlet obstruction or dyskaryotic complement.

Diagnosis

The diagnosis of discordant anomalous twin is made by ultrasound. Please refer to our other webpages for information on the diagnosis of Stage III & 4 TTTS, Acardiac Twin, severe IUGR, bladder outlet obstruction and PROM.

Assessment of discordant anomalous twins for in utero therapy

In utero therapy is usually limited to the ultrasonographic noting of the following characteristics:

• TRAP sequence: polyhydramnios (maximum vertical pocket ≥ 8cm), large TRAP fetus (ratio of abdominal circumference of TRAP fetus/ abdominal circumference of pump fetus ≥ 1 or estimated fetal weight TRAP fetus/ pump fetus ≥1), monoamniotic TRAP pregnancy
• Anencephaly
• Other lethal twin conditions
• Stage III-IV twin-twin transfusion syndrome
• Congestive heart failure of one twin as evidenced by overt hydrops, or third spacing
• Reverse flow in the ductus venosus or reverse umbilical venous flow
• Cord entanglement
• Non-lethal discordant anomalous twins
• Dyskaryotic twins
• Premature previable (<22 weeks) PROM of twin A
• Monoamniotic twin-twin transfusion syndrome

Patients with any of the above conditions may present with additional complicating factors that may add to the criteria for surgery. These include: polyhydramnios (maximum vertical pocket > 8 cm), short cervical length (cervix <2.5 cm via transvaginal ultrasound), maternal symptoms of preterm labor.

Treatment of discordant anomalous twins

Suture umbilical cord occlusion (UCL)

Under local anesthesia and with continuous ultrasound guidance, a 3.5-mm trocar is inserted into the uterine cavity. Umbilical cord occlusion using ligature (UCL) is accomplished by passing a 3-0 Vicryl suture around the target umbilical cord and tying an extracorporeal knot. In the original technique, two ports were required. This was modified to include a single port, combining ultrasound and endoscopic guidance.

Umbilical cord occlusion via photocoagulation of the cord (UCP)

Laser photocoagulation of the umbilical cord is performed under endoscopic guidance as an alternative to UCL. The umbilical cord artery and vein are photocoagulated using 20-40 Watts of Nd: YAG laser energy via a 600 μ fiber through an operating endoscope.

Transection of Umbilical Cord (UCL&T)

Umbilical cord transection was developed after noting demise from cord entanglement from purposeful dividing membrane amniorrhexis. The technique is also applicable to monoamniotic patients. The cord is transected closest to the discordant/anomalous fetus using scissors or YAG-laser energy through a 600μ contact fiber after placing 2-3 individual knots.

Laser photocoagulation of the arterio-arterio and veno-venous anastomoses (L-AAVV)

Laser photocoagulation of the corresponding arterio-arterio (AA) and veno-venous (VV) (L-AAVV) anastomosis was first described by Hecher et al. We elect to perform this technique if prominent AA and VV anastomoses can be distinctly identified, and if the cords do not seem too close to each other, risking thermal damage to the normal twin's cord. The AA anastomosis is photocoagulated first, followed by the VV anastomosis.

Referrals

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