**6.1 Twin gestations**

## *6.1.1 Twin–twin transfusion syndrome (TTTS)*

Monochorionic (shared) placenta with A-V, V-V, A-A connections and unbalanced flow between two twins


Prognosis: 80–90% mortality for both if untreated.

Fetal Surgery


Offered to Stage II or greater Selective A-V or nonselective

76% single survivor, 36% dual survivors.

The donor twin usually develops hypovolemia, leading to oliguria and oligohydramnios from reduced renal perfusion, and the recipient twin suffers the consequences of hypervolemia, including polyuria and polyhydramnios. Both twins are at risk for significant morbidity [41, 42].

Basic principles for TTTS interventions are to prevent preterm delivery caused by polyhydramnios, through removing the excess amniotic fluid surrounding

**9**

**Table 4.** *Staging of TTTS.*

(**Table 4**) [43–45].

V Fetal death

anastomoses

*6.1.2 Twin reversed arterial perfusion*

I Presence of Poly and oligohydramnios

II Stage I plus non-visualized bladder in donor twin

IV Stage III plus evidence of hydrops in either twin

ductus venosus reversed flow, pulsatile umbilical venous flow)

*Principles of Fetal Surgery*

**I-Surgery on the fetus**

*DOI: http://dx.doi.org/10.5772/intechopen.85883*

**II- Placenta, cord or membranes surgery**

Complicated monochorionic

Twin–twin transfusion syndrome

Twin-reversed-arterial-perfusion

(TRAP) and other discordant

Twin-anemia polycythaemia

**III- Selective intra-uterine growth restriction**

*Some important indications for fetal surgery.*

pregnancies:

(TTTS)

sequence

anomalies

sequence

**Table 3.**

**Fetal surgery Why to interfere?**

the recipient twin, with improved fetal circulation by decreasing pressure on the chorionic plate. In 1990, fetoscopic laser was used to coagulate the crossing superficial blood vessels separating the 2 fetal circulations and destroying the inter-twin vessels that cause discordant twin–twin transfusion. Nowadays, laser ablation is the preferred treatment for TTTS between 16 and 26 weeks of gestation. The procedure is performed through a single uterine access site using a fetoscope and thin laser

Chorioangioma Avoid of cardiac failure, hydrops fetoplacental and polyhydramnios

Congenital diaphragmatic hernia Avoidance of pulmonary hypoplasia and pulmonary hypertension Sacrococcygeal teratoma Stop of steal phenomenon, avoid cardiac failure and polyhydramnios

Cardiac malformations Avoid hypoplasia or progressing damage to developing heart Myelomeningocele Repair of exposed spinal nerves, stop cerebrospinal fluid leakage,

Avoid preterm delivery

Avoid damage to co-twin

polyhydramnios

Amniotic band syndrome Avoid deformities and functional loss

prevent hydrocephaly and hindbrain herniation

Arrest of feto-fetal transfusion and its consequences

In some conditions (TTTS/TRAP) reversal of cardiac failure and

Thoracic space-occupying lesions Avoid pulmonary hypoplasia and cardiac failure Lower urinary tract obstruction Avoid renal failure and pulmonary hypoplasia

One normal twin acts as a "pump" for a cardiac, a cephalic twin via A-A

III Stage II plus seriously abnormal Doppler (umbilical artery absent or reversed end-diastolic velocity,


#### **Table 3.**

*Pediatric Surgery, Flowcharts and Clinical Algorithms*

premature rupture of membranes [36–38].

procedures should be considered [39, 40].

*6.1.1 Twin–twin transfusion syndrome (TTTS)*

**6.1 Twin gestations**

anced flow between two twins

ischemia, small

fetalis, large

Fetal Surgery

**6. Certain problems amenable for fetal surgery**

Prognosis: 80–90% mortality for both if untreated.

• Fetoscopic laser ablation of vascular connections

Offered to Stage II or greater Selective A-V or nonselective

at risk for significant morbidity [41, 42].

76% single survivor, 36% dual survivors.

due to variations in both the assessment of the complication as well as reporting methods. Factors increasing the risk during minimally invasive fetal procedures include the number of ports and the diameter of the used instruments. A systematic review of 1376 minimally invasive fetal procedures for lower urinary tract obstruction, and twin reversed arterial perfusion reported that increased diameter of the instrument and increased number of ports are major predictors of iatrogenic

Following open fetal procedure, risk of hysterotomy scar weakness may interrupt both current and future labor. Some cases of uterine scar rupture after open fetal procedure was reported, starting from the second trimester, may be caused only by the uterine distension (with no uterine contractions) which form significant risk to both mother and fetus. Moreover, maternal counseling about the risk of delivery complications must be considered. On the other hand, minimally invasive fetal procedures do not preclude vaginal delivery. However, long-term follow-up of subsequent pregnancies after these procedures is not available, beside the complications of repeat caesarian section, significant advantage of minimally invasive fetal

Some important indications for fetal interventions are summarized in **Table 3**.

Monochorionic (shared) placenta with A-V, V-V, A-A connections and unbal-

• Recipient – fluid overload, polyhydramnios, congestive heart failure, hydrops

• High-volume amnioreduction historically (survival of at least one twin 60%)

The donor twin usually develops hypovolemia, leading to oliguria and oligohydramnios from reduced renal perfusion, and the recipient twin suffers the consequences of hypervolemia, including polyuria and polyhydramnios. Both twins are

Basic principles for TTTS interventions are to prevent preterm delivery caused

by polyhydramnios, through removing the excess amniotic fluid surrounding

• Donor – low flow, oligohydramnios, high output heart failure, brain

**8**

*Some important indications for fetal surgery.*

the recipient twin, with improved fetal circulation by decreasing pressure on the chorionic plate. In 1990, fetoscopic laser was used to coagulate the crossing superficial blood vessels separating the 2 fetal circulations and destroying the inter-twin vessels that cause discordant twin–twin transfusion. Nowadays, laser ablation is the preferred treatment for TTTS between 16 and 26 weeks of gestation. The procedure is performed through a single uterine access site using a fetoscope and thin laser (**Table 4**) [43–45].
