Sequential vs. Standard Laser Treatment of Twin-twin Transfusion Syndrome

Inclusion Criteria: * Gestational age: 16 weeks, 0 days to 26 weeks, 0 days. * Confirmed TTTS patients, who by definition meet the following sonographic criteria: * Single placenta. * Polyhydramnios: maximum vertical pocket ≥ 8 cm in the recipient twin, prior to amniodrainage. * Oligohydramnios: maximum vertical pocket ≤ 2 cm in the donor twin, prior to amniodrainage. * Thin dividing membrane (absence of twin peak sign) or absence of dividing membrane (monoamniotic). * Same gender, if visible. * Quintero Stages 1-4. * Patients choosing laser therapy that have undergone prior therapeutic amniocentesis may be included. * Patients with an anterior placenta may be included. * Triplet gestations with two or three fetuses sharing the same placenta may be included. * Patients must be able to give written informed consent. Exclusion Criteria: * Patients unable or unwilling to participate in the study or to be followed up. * Patients unable to give written informed consent. * Presence of major congenital anomalies that may not warrant surgery. * Known unbalanced chromosomal complement. * Prior intentional septostomy (purposely making a hole in the dividing membrane). * Ruptured membranes. * Chorioamnionitis. * Abnormal intracranial ultrasound findings of either fetus to include, but not limited to: intraventricular hemorrhage, porencephalic cysts, hydrocephalus, Dandy-Walker syndrome, holoprosencephaly and agenesis of the corpus callosum. Isolated ventriculomegaly (atrium 10-19 mm) may or may not be used as exclusion criteria. * Placental abruption. * Active labor. * Patient unwilling to receive blood products. * Recipient twin with a middle cerebral artery peak systolic velocity \> 1.5 multiples of the median (indicative of fetal anemia). * Any other patient deemed inappropriate for the study by the principal investigator.