Patients will undergo an intake evaluation followed by a detailed ultrasound examination to rule out the presence of congenital anomalies and to assess the hemodynamic status of the fetuses and any pre-existing cerebral damage. The following data will be collected, as is identical to the standard of care in evaluating monochorionic twins
Maternal
- Age
- Gravidity and parity
- BMI
- Race/ethnicity
- Gestational age
- The presence of any symptoms
- Cervical length
Fetal
- Estimated fetal weight
- Detailed anatomy
- Doppler evaluation of umbilical cord, ductus venosus and middle cerebral arteries
- Evaluation of the myocardial performance indices
- Amniotic fluid volume
- Placental position
- Cord insertions
Patients will then be counseled about the risks and benefits of the procedure and will be asked to sign an informed consent.
The procedure will be performed under a spinal or local anesthesia at the discretion of the anesthesiologist and surgeon based upon placental position, maternal hemodynamic stability and maternal anxiety and ability to cooperate. Ultrasound guidance will help to select an appropriate incisional site. Under ultrasound guidance, a 2 mm skin incision will be made and a 10 French Cook Check Flow valve cannula and trocar will be introduced into the amniotic cavity. An amniotic fluid sample will be obtained and sent for microbiological studies. A small aliquot of fluid will also be set aside for future institutional review board approved studies (see detail regarding banking below).
The communicating vessels will be located endoscopically using a Storz straight or curved semirigid fetoscopes in a fetoscopic sheath, a Humanitarian Use Device, used with permission of the Federal Drug Administration under a Humanitarian Device Exemption agreement with Karl Storz, Inc, and will be ablated with a diode laser fiber that is passed through the operating channel of the endoscope. The Laser used is a Dornier Diode laser using a power of 30-40 Watts. At the conclusion of the anastomotic ablation, an ablation line will be created across the vascular equator, effectively dichorionizing the placenta. The procedure will be monitored both endoscopically and sonographically. The presence of fetal heart activity will be documented at the beginning and end of the procedure. An amniodrainage of the larger sac will be performed at the conclusion of the procedure to leave the amniotic fluid volume of that sac at a normal level.
